Class 7 Olympiad Previous Years Question Bank & Solved Papers

IMO Olympiad Year 2024 Class 7 60 Mins · 50 Marks ✓ Verified Solutions

International Mathematics Olympiad (IMO) - Class 7 Solved Paper

Class 7 IMO championship paper focusing on rational numbers, exponents and powers, algebraic expressions, linear equations in one variable, triangle congruence, angles, simple interest, data handling, and higher order logic.

Topics Covered: Integers & Rationals Exponents & Powers Linear Equations Lines, Angles & Congruence Simple Interest Perimeter & Area Blood Relations & Venn Diagrams Achievers HOTS

Question 1 Mathematical Reasoning

1 Mark

Evaluate the expression: (-1)^101 + (-1)^102 + (-1)^103 + ... + (-1)^200.

A -1

B 0 ✓ Correct

C 1

D 100

Concept Tested: Powers of -1 and pairing consecutive odd-even exponents

Hint: (-1)^odd = -1 and (-1)^even = +1. Count how many total terms there are.

Detailed Step-by-Step Verified Solution

Step 1: Total terms from 101 to 200 = (200 - 101 + 1) = 100 terms.
Step 2: Notice consecutive pairs: (-1)^101 + (-1)^102 = (-1) + (+1) = 0.
Step 3: Since there are exactly 100 terms, there are 50 pairs, each summing to 0.
Step 4: Total sum = 50 × 0 = 0.

Official Final Answer: Correct Option (B) : 0

💡 Olympiad Tip & Strategy: Always compute total terms using N = (Last - First + 1).

Question 2 Mathematical Reasoning

1 Mark

If (2/3)^3 × (2/3)^-6 = (2/3)^(2x - 1), find the value of x.

A -1 ✓ Correct

B 1

C -2

D 2

Concept Tested: Laws of Exponents: a^m × a^n = a^(m+n) and equating powers of equal bases

Hint: Combine LHS powers: 3 + (-6) = -3. Then equate with 2x - 1.

Detailed Step-by-Step Verified Solution

Step 1: Apply product law on LHS: (2/3)^(3 + (-6)) = (2/3)^(-3).
Step 2: Since bases are identical and non-zero, equate exponents: -3 = 2x - 1.
Step 3: 2x = -3 + 1 = -2 => x = -1.

Official Final Answer: Correct Option (A) : -1

💡 Olympiad Tip & Strategy: Check whether base is -1, 0, or 1 before equating exponents directly.

Question 3 Achievers Section (HOTS)

3 Marks

Two supplementary angles are in the ratio 7 : 11. What is the measure of the complementary angle of the smaller angle?

A 70°

B 20° ✓ Correct

C 35°

D 40°

Concept Tested: Supplementary angles (sum 180°) vs Complementary angles (sum 90°)

Hint: 7x + 11x = 180°. Find smaller angle, then compute 90° - that angle.

Detailed Step-by-Step Verified Solution

Step 1: Supplementary angles sum to 180°: 7x + 11x = 180° => 18x = 180° => x = 10°.
Step 2: Smaller angle = 7 × 10° = 70° (larger angle = 110°).
Step 3: The complementary angle of the smaller angle is: 90° - 70° = 20°.

Official Final Answer: Correct Option (B) : 20°

💡 Olympiad Tip & Strategy: Olympiad questions test multi-stage definitions: supplementary first, then complementary!

Question 4 Logical Reasoning

1 Mark

Pointing to a gentleman, Deepak said, "His only brother is the father of my daughter's father." How is the gentleman related to Deepak?

A Father

B Uncle (Paternal) ✓ Correct

C Grandfather

D Brother

Concept Tested: Blood relations and reverse decoding of family relations

Hint: "My daughter's father" is Deepak himself. So the gentleman's only brother is Deepak's father.

Detailed Step-by-Step Verified Solution

Step 1: Break down Deepak's statement from the end: "my daughter's father" is Deepak himself.
Step 2: "Father of my daughter's father" means father of Deepak.
Step 3: "His only brother is Deepak's father" means the gentleman is the brother of Deepak's father.
Step 4: The brother of one's father is one's paternal uncle.

Official Final Answer: Correct Option (B) : Uncle (Paternal)

💡 Olympiad Tip & Strategy: In blood relations, substitute your own self in place of the speaker to quickly identify relationships.

Question 5 Logical Reasoning

1 Mark

In a class of 50 students, 30 play Cricket, 25 play Football, and 12 play both games. How many students play neither Cricket nor Football?

A 7 ✓ Correct

B 5

C 10

D 8

Concept Tested: Set theory and Venn diagram: n(A ∪ B) = n(A) + n(B) - n(A ∩ B)

Hint: Find students who play at least one sport: 30 + 25 - 12 = 43.

Detailed Step-by-Step Verified Solution

Step 1: Total students playing at least one game = n(Cricket) + n(Football) - n(Both).
Step 2: n(Cricket ∪ Football) = 30 + 25 - 12 = 55 - 12 = 43 students.
Step 3: Students playing neither game = Total students - 43 = 50 - 43 = 7 students.

Official Final Answer: Correct Option (A) : 7

💡 Olympiad Tip & Strategy: Venn diagrams prevent double counting the intersection.

Question 6 Mathematical Reasoning

1 Mark

Find the value of x such that: (3x - 2)/4 - (2x + 3)/3 = 2/3 - x.

A 2 ✓ Correct

B 3

C 4

D 1

Concept Tested: Linear equations in one variable with fractional coefficients

Hint: Multiply the entire equation by the LCM of 3 and 4, which is 12.

Detailed Step-by-Step Verified Solution

Step 1: Multiply every term by 12:
3(3x - 2) - 4(2x + 3) = 4(2) - 12x.
Step 2: Expand the parentheses: 9x - 6 - 8x - 12 = 8 - 12x.
Step 3: Combine like terms: x - 18 = 8 - 12x.
Step 4: Transpose variables: x + 12x = 8 + 18 => 13x = 26 => x = 2.

Official Final Answer: Correct Option (A) : 2

💡 Olympiad Tip & Strategy: Multiplying by the global LCM clears all denominators in one single step!

Question 7 Mathematical Reasoning

1 Mark

In a triangle, an exterior angle measures 115° and one of the interior opposite angles measures 45°. What is the measure of the other interior opposite angle?

A 70° ✓ Correct

B 65°

C 60°

D 75°

Concept Tested: Exterior angle property of a triangle: Exterior = Sum of interior opposites

Hint: Exterior angle = ∠1 + ∠2 => 115° = 45° + x.

Detailed Step-by-Step Verified Solution

Step 1: Recall the Exterior Angle Theorem: The exterior angle of a triangle is equal to the sum of its two interior opposite angles.
Step 2: 115° = 45° + x.
Step 3: x = 115° - 45° = 70°.

Official Final Answer: Correct Option (A) : 70°

💡 Olympiad Tip & Strategy: Exterior angle is always strictly greater than either of its opposite interior angles.

Question 8 Mathematical Reasoning

1 Mark

At what rate percent per annum simple interest will a sum of money double itself in 8 years?

A 12.5% ✓ Correct

B 10%

C 15%

D 16.67%

Concept Tested: Simple interest and principal doubling formula: Rate = 100 / T

Hint: If Principal is P, Amount is 2P, so SI = P. Formula: R = (SI × 100) / (P × T).

Detailed Step-by-Step Verified Solution

Step 1: Let the principal be P. When it doubles, Amount = 2P.
Step 2: Simple Interest SI = Amount - Principal = 2P - P = P.
Step 3: Use SI formula: SI = (P × R × T) / 100.
P = (P × R × 8) / 100 => 1 = 8R / 100.
Step 4: R = 100 / 8 = 12.5% per annum.

Official Final Answer: Correct Option (A) : 12.5%

💡 Olympiad Tip & Strategy: Olympiad shortcut for doubling time in SI: Rate × Time = 100.

Question 9 Mathematical Reasoning

1 Mark

If triangle ABC is congruent to triangle PQR under the correspondence ABC ↔ PQR, and ∠A = 50°, ∠B = 60°, what is the measure of ∠R?

A 70° ✓ Correct

B 60°

C 50°

D 80°

Concept Tested: Angle sum property of triangle and CPCTC (Corresponding Parts of Congruent Triangles)

Hint: First find ∠C = 180° - (50° + 60°). Then ∠R = ∠C.

Detailed Step-by-Step Verified Solution

Step 1: In triangle ABC, sum of angles is 180°: ∠C = 180° - (50° + 60°) = 180° - 110° = 70°.
Step 2: Given ΔABC ≅ ΔPQR, corresponding angles are equal: ∠R = ∠C.
Step 3: Therefore ∠R = 70°.

Official Final Answer: Correct Option (A) : 70°

💡 Olympiad Tip & Strategy: Correspondence order matters: A ↔ P, B ↔ Q, C ↔ R.

Question 10 Everyday Mathematics / Science

1 Mark

A wire is in the shape of a square of side 22 cm. If the wire is rebent into the shape of a circle, what is the radius of the circle formed? (Take π = 22/7)

A 14 cm ✓ Correct

B 7 cm

C 21 cm

D 28 cm

Concept Tested: Conservation of perimeter when rebending wire: Perimeter of Square = Circumference of Circle

Hint: Total length of wire = 4 × 22 = 88 cm. Set 2πr = 88.

Detailed Step-by-Step Verified Solution

Step 1: Length of wire = Perimeter of square = 4 × 22 cm = 88 cm.
Step 2: When rebent into a circle, Circumference = Length of wire: 2 × π × r = 88 cm.
Step 3: 2 × (22/7) × r = 88 => (44/7) × r = 88.
Step 4: r = (88 × 7) / 44 = 2 × 7 = 14 cm.

Official Final Answer: Correct Option (A) : 14 cm

💡 Olympiad Tip & Strategy: The area of the circle formed is strictly larger than the square, even though perimeter is identical!

Question 11 Everyday Mathematics / Science

1 Mark

The mean of 5 numbers is 27. If one number is excluded, their mean becomes 25. What is the excluded number?

A 35 ✓ Correct

B 30

C 25

D 40

Concept Tested: Statistical mean and sum of observations

Hint: Sum of 5 numbers = 5 × 27. Sum of remaining 4 numbers = 4 × 25.

Detailed Step-by-Step Verified Solution

Step 1: Total sum of original 5 numbers = Mean × Count = 27 × 5 = 135.
Step 2: Total sum of remaining 4 numbers = 25 × 4 = 100.
Step 3: Excluded number = (Sum of 5) - (Sum of 4) = 135 - 100 = 35.

Official Final Answer: Correct Option (A) : 35

💡 Olympiad Tip & Strategy: Always convert averages back into sums to solve addition/exclusion problems.

Question 12 Achievers Section (HOTS)

3 Marks

If 2^(x - 1) + 2^(x + 1) = 320, find the value of the integer x.

A 7 ✓ Correct

B 6

C 8

D 5

Concept Tested: Factoring common terms in exponential equations

Hint: Factor out 2^(x - 1): 2^(x-1) [1 + 2^2] = 320.

Detailed Step-by-Step Verified Solution

Step 1: Rewrite terms using base powers: 2^(x+1) = 2^(x-1) × 2^2 = 4 × 2^(x-1).
Step 2: Substitute into equation: 2^(x-1) + 4 × 2^(x-1) = 5 × 2^(x-1).
Step 3: 5 × 2^(x-1) = 320 => 2^(x-1) = 320 ÷ 5 = 64.
Step 4: Express 64 as a power of 2: 64 = 2^6.
Step 5: Equate exponents: x - 1 = 6 => x = 7.

Official Final Answer: Correct Option (A) : 7

💡 Olympiad Tip & Strategy: Factoring out the lowest power simplifies exponential equations immediately.

Question 13 Achievers Section (HOTS)

3 Marks

If a + b + c = 0, what is the value of: (a²/bc) + (b²/ca) + (c²/ab)?

A 3 ✓ Correct

B 0

C 1

D -3

Concept Tested: Special algebraic identity: If a + b + c = 0, then a³ + b³ + c³ = 3abc

Hint: Take LCM of denominators: abc. Numerator becomes a³ + b³ + c³.

Detailed Step-by-Step Verified Solution

Step 1: Combine the three fractions with a common denominator of abc:
(a²·a + b²·b + c²·c) / (abc) = (a³ + b³ + c³) / (abc).
Step 2: Standard algebraic theorem: When a + b + c = 0, then a³ + b³ + c³ = 3abc.
Step 3: Substitute 3abc in the numerator: (3abc) / (abc) = 3.

Official Final Answer: Correct Option (A) : 3

💡 Olympiad Tip & Strategy: This famous identity is a cornerstone of Olympiad algebra across Class 7 to 10.

NSO Olympiad Year 2024 Class 7 60 Mins · 50 Marks ✓ Verified Solutions

National Science Olympiad (NSO) - Class 7 Solved Paper

Class 7 NSO paper covering nutrition in plants (parasitic nutrition), heat transfer mechanisms (sea/land breeze), acids, bases & indicators (China rose, calamine neutralization), respiration, transportation in plants (xylem/phloem), reproduction, simple pendulum, spherical mirrors, and electromagnetism.

Topics Covered: Nutrition in Living Organisms Heat & Temperature Acids, Bases & Salts Physical & Chemical Changes Motion & Time Respiration & Transportation Reproduction in Plants Light & Optics Achievers HOTS

Question 1 Scientific Reasoning

1 Mark

When China rose indicator solution is added to a test tube containing dilute hydrochloric acid, what color change is observed?

A Turns dark pink (magenta) ✓ Correct

B Turns green

C Remains light yellow

D Turns milky white

Concept Tested: Natural indicators: China rose petal extract behavior in acidic and basic media

Hint: China rose turns acidic solutions dark pink (magenta) and basic solutions green.

Detailed Step-by-Step Verified Solution

Step 1: Identify the reagent: Dilute hydrochloric acid is an acidic solution (pH < 7).
Step 2: China rose (Hibiscus) indicator is naturally light pink.
Step 3: In an acidic medium, it turns dark pink (magenta). In a basic medium, it turns green.

Official Final Answer: Correct Option (A) : Turns dark pink (magenta)

💡 Olympiad Tip & Strategy: Remember: Turmeric turns reddish-brown in base, but stays yellow in acid!

Question 2 Achievers Section (HOTS)

3 Marks

An electric bell rings continuously when the switch is pressed because of:

A Heating effect of electric current melting the contact

B Electromagnet attracting the soft iron armature, which breaks the contact and repeatedly resets the circuit ✓ Correct

C Chemical decomposition of the wire creating acoustic waves

D Electrostatic repulsion between gong and hammer

Concept Tested: Electromagnetism and make-and-break circuit mechanism of electric bell

Hint: When current flows, electromagnet pulls the armature, striking the gong while simultaneously breaking the contact.

Detailed Step-by-Step Verified Solution

Step 1: Pressing the switch completes the circuit, energizing the electromagnet.
Step 2: The soft iron armature is pulled towards the electromagnet, striking the brass gong with the attached hammer.
Step 3: This forward movement pulls the contact spring away from the contact screw, opening the circuit.
Step 4: The electromagnet loses magnetism, the spring returns the armature back, closing the circuit again in rapid repetition.

Official Final Answer: Correct Option (B) : Electromagnet attracting the soft iron armature, which breaks the contact and repeatedly resets the circuit

💡 Olympiad Tip & Strategy: This self-interrupting mechanism is the classic example of magnetic feedback in circuits.

Question 3 Scientific Reasoning

1 Mark

Cuscuta (Amarbel) is an example of which type of organism?

A Autotroph

B Parasite ✓ Correct

C Saprotroph

D Symbiont

Concept Tested: Heterotrophic nutrition in plants: Parasitism in non-green plants

Hint: Cuscuta lacks chlorophyll and absorbs nutrients directly from the host plant through haustoria.

Detailed Step-by-Step Verified Solution

Step 1: Cuscuta is a yellow tubular climbing plant that does not have chlorophyll.
Step 2: It climbs onto green trees (host plants) and inserts specialized sucking roots called haustoria into the vascular bundles of the host.
Step 3: Because it derives readymade food at the expense of the host without giving any benefit, it is a parasitic plant.

Official Final Answer: Correct Option (B) : Parasite

💡 Olympiad Tip & Strategy: Fungi (mushrooms) are saprotrophs because they feed on dead decaying matter; Cuscuta feeds on living hosts.

Question 4 Scientific Reasoning

1 Mark

During heavy strenuous exercise, we sometimes get painful muscle cramps. This is primarily caused by the partial breakdown of glucose into:

A Alcohol and Carbon dioxide

B Lactic acid ✓ Correct

C Water and Carbon dioxide

D Glucose and Oxygen

Concept Tested: Anaerobic respiration in human skeletal muscles during oxygen deficiency

Hint: In absence of adequate oxygen, muscle cells convert pyruvate into lactic acid.

Detailed Step-by-Step Verified Solution

Step 1: In heavy exercise, demand for energy is high but oxygen supply is limited.
Step 2: Muscle cells perform temporary anaerobic respiration.
Step 3: Glucose breaks down into lactic acid: Glucose -> Lactic acid + Energy.
Step 4: The accumulation of lactic acid crystals in muscle fibres causes painful cramps.

Official Final Answer: Correct Option (B) : Lactic acid

💡 Olympiad Tip & Strategy: A hot water bath or gentle massage improves blood circulation, restoring oxygen and breaking down lactic acid.

Question 5 Scientific Reasoning

1 Mark

Which specialized vascular tissue in plants is responsible for transporting water and dissolved mineral salts unidirectionally from roots to leaves?

A Phloem

B Xylem ✓ Correct

C Cortex

D Stomata

Concept Tested: Plant vascular anatomy: Xylem vs Phloem

Hint: Xylem conducts water/minerals upwards; Phloem translocates sucrose/food bidirectionally.

Detailed Step-by-Step Verified Solution

Step 1: Plants absorb water and mineral salts from the soil via root hairs.
Step 2: Xylem forms continuous capillary tubes running from roots through stem into leaves.
Step 3: Transpiration pull generates suction pulling water upwards in a single unidirectional upward path through xylem.

Official Final Answer: Correct Option (B) : Xylem

💡 Olympiad Tip & Strategy: Remember the mnemonic: "Xylem for Xylophone (Water) - Phloem for Food".

Question 6 Scientific Reasoning

1 Mark

In coastal areas, during daytime, cool breeze blows from the sea towards the land. This phenomenon is called:

A Sea Breeze caused by convection currents ✓ Correct

B Land Breeze caused by radiation

C Cyclone caused by low pressure

D Monsoon caused by conduction

Concept Tested: Heat capacity of water vs land and convection currents in coastal regions

Hint: Land heats faster than water during the day, creating low pressure over land.

Detailed Step-by-Step Verified Solution

Step 1: Specific heat capacity of water is higher than land; hence land heats up much faster during the day.
Step 2: Air above land becomes warm and rises, creating a low-pressure zone.
Step 3: Cooler, denser air from above the sea moves in to take its place, forming the Sea Breeze.

Official Final Answer: Correct Option (A) : Sea Breeze caused by convection currents

💡 Olympiad Tip & Strategy: At night, the reverse happens: Land cools faster, resulting in Land Breeze (Land to Sea).

Question 7 Scientific Reasoning

1 Mark

Bryophyllum reproduces vegetatively through which of its plant parts?

A Roots

B Stem cuttings

C Buds present in the notches of leaf margins ✓ Correct

D Spores produced in sporangia

Concept Tested: Asexual reproduction in plants: Vegetative propagation through leaves

Hint: Bryophyllum leaves develop adventitious buds along their notched serrated edges.

Detailed Step-by-Step Verified Solution

Step 1: Bryophyllum has fleshy broad leaves with notches along the edges.
Step 2: In the notches, adventitious buds arise.
Step 3: When a leaf falls on moist soil, each bud sprouts tiny roots and shoots, growing into an independent new plant.

Official Final Answer: Correct Option (C) : Buds present in the notches of leaf margins

💡 Olympiad Tip & Strategy: Ginger reproduces through rhizome; Potato reproduces through "eyes" (buds on stem tuber).

Question 8 Scientific Reasoning

1 Mark

A simple pendulum takes 32 seconds to complete 20 full oscillations. What is the time period of the pendulum?

A 1.6 seconds ✓ Correct

B 0.625 seconds

C 3.2 seconds

D 2.0 seconds

Concept Tested: Simple pendulum time period: T = Total Time ÷ Number of Oscillations

Hint: Time period is the time taken for ONE complete oscillation: 32 ÷ 20.

Detailed Step-by-Step Verified Solution

Step 1: By definition, Time Period (T) = Total time taken / Number of oscillations.
Step 2: T = 32 seconds ÷ 20 = 1.6 seconds.
Step 3: The pendulum completes one oscillation in 1.6 s.

Official Final Answer: Correct Option (A) : 1.6 seconds

💡 Olympiad Tip & Strategy: Time period of a simple pendulum depends only on its length, not on the mass of the bob.

Question 9 Scientific Reasoning

1 Mark

Which of the following processes represents a chemical change where a new substance is formed with entirely different properties?

A Melting of ice cubes

B Rusting of an iron gate exposed to moist air ✓ Correct

C Dissolving sugar in water

D Tearing a sheet of paper into small pieces

Concept Tested: Physical vs Chemical changes in matter

Hint: Chemical changes are irreversible and produce new chemical bonds (e.g. Iron oxide Fe2O3·xH2O).

Detailed Step-by-Step Verified Solution

Step 1: Melting, dissolving, and tearing alter physical state or appearance without changing chemical composition (physical changes).
Step 2: When iron reacts with atmospheric oxygen and moisture: 4Fe + 3O2 + 2xH2O -> 2Fe2O3·xH2O (Rust).
Step 3: Rust is chemically different from iron, magnetic properties change, and the process is irreversible.

Official Final Answer: Correct Option (B) : Rusting of an iron gate exposed to moist air

💡 Olympiad Tip & Strategy: Galvanization (zinc coating) prevents iron from contacting oxygen and moisture.

Question 10 Everyday Science

1 Mark

Which layer of forest vegetation is formed by the crowns of tall trees touching each other and acting as a roof over the lower plants?

A Understorey

B Canopy ✓ Correct

C Forest Floor

D Humus layer

Concept Tested: Forest ecosystem stratification: Canopy vs Understorey

Hint: The continuous upper roof formed by leaves and branches of tallest trees is the canopy.

Detailed Step-by-Step Verified Solution

Step 1: The highest branches and foliage of tall trees meet to form an overhead ceiling called the canopy.
Step 2: Below the canopy lies the understorey consisting of shrubs, small trees, and saplings.
Step 3: The ground layer is the forest floor covered with dead leaves and decomposers.

Official Final Answer: Correct Option (B) : Canopy

💡 Olympiad Tip & Strategy: Canopy absorbs most sunlight; understorey plants are adapted to survive in lower light levels.

Question 11 Achievers Section (HOTS)

3 Marks

Why are convex mirrors universally preferred as rear-view mirrors in motor vehicles?

A They form real and magnified images

B They always form erect, virtual, and diminished images, providing a much wider field of view ✓ Correct

C They invert the image to correct driver perception

D They focus distant light rays onto a single spot

Concept Tested: Spherical mirror optics and wide field of view of convex mirrors

Hint: Convex mirrors curve outward, shrinking images so more traffic fits in the mirror.

Detailed Step-by-Step Verified Solution

Step 1: A convex mirror curves outward away from the center of curvature.
Step 2: For any object position, it always forms a virtual, erect, and diminished (smaller) image behind the mirror.
Step 3: Because images are diminished and the surface curves outward, it captures light from a vastly wider field of view than a plane mirror of the same size.

Official Final Answer: Correct Option (B) : They always form erect, virtual, and diminished images, providing a much wider field of view

💡 Olympiad Tip & Strategy: Dentists use concave mirrors because concave mirrors produce magnified images when held close!

Question 12 Achievers Section (HOTS)

3 Marks

An ant sting injects an acidic liquid into the skin causing severe irritation and burning. The effect can be neutralized by rubbing the skin with moist baking soda or calamine solution because:

A The sting contains formic acid (methanoic acid), and calamine contains basic zinc carbonate which neutralizes it ✓ Correct

B The sting contains sodium hydroxide, which is neutralized by acetic acid

C Calamine creates an ice-cold layer that numbs nerve receptors

D Ant venom is an oil that dissolves in ethanol

Concept Tested: Acid-base neutralization in biological systems

Hint: Formic acid (HCOOH) is neutralized by a mild base such as baking soda (NaHCO3) or zinc carbonate (ZnCO3).

Detailed Step-by-Step Verified Solution

Step 1: Ant venom contains formic acid (methanoic acid, HCOOH).
Step 2: To relieve the burning sensation, a mild non-corrosive base is applied.
Step 3: Calamine solution contains zinc carbonate (ZnCO3), and baking soda is sodium hydrogen carbonate (NaHCO3).
Step 4: The base neutralizes the acid: Acid + Base -> Salt + Water, ending the irritation.

Official Final Answer: Correct Option (A) : The sting contains formic acid (methanoic acid), and calamine contains basic zinc carbonate which neutralizes it

💡 Olympiad Tip & Strategy: Wasp stings are alkaline and must be neutralized with a mild acid like vinegar!