Class 4 NSO practice paper

Class 4 NSO Olympiad Practice Questions
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Class 4 NSO Practice Paper 2026: Sample Questions, Answer Key & Explanations

 

Download the complete Class 4 National Science Olympiad (NSO) practice paper with answers and step-by-step explanations. Ideal for SOF Class 4 NSO exam preparation.

 

SECTION 1: LOGICAL REASONING

Q1. In a certain code language, if ‘PLANT’ is coded as ‘QMBOU’, then how will ‘SOLAR’ be coded in that same language?

  1. TPMBS
  2. TPKBS
  3. TNMBS
  4. SPMBR

Q2. Trisha is facing North. She first turns 3/4 turn to her right and then 1/2 turn to her left. Which direction is she facing now?

  1. East
  2. West
  3. North
  4. South

Q3. Find the missing number in the given number pattern:
4,  8,  16,  32,  ?,  128

  1. 48
  2. 64
  3. 52
  4. 96

Q4. How many line segments are required to form a closed square figure?

  1. 2
  2. 3
  3. 4
  4. 5

Q5. Select the odd one out from the given options.

  1. River
  2. Lake
  3. Pond
  4. Mountain

SECTION 2: SCIENCE

Q6. Which of the following raw materials is NOT taken up from the surrounding environment by plants to prepare food during photosynthesis?

  1. Water
  2. Carbon dioxide
  3. Sunlight
  4. Oxygen

Q7. Which of the following food chains correctly represents a valid natural ecological flow?

  1. Grass → Grasshopper → Frog → Snake
  2. Wheat → Snake → Grasshopper → Frog
  3. Mango → Caterpillar → Bird → Monkey
  4. Grass → Lion → Rabbit → Fox

Q8. Which organ system in the human body is responsible for transporting oxygen, nutrients, and metabolic waste throughout the body?

  1. Respiratory system
  2. Circulatory system
  3. Digestive system
  4. Excretory system

Q9. Mangrove trees grow in swampy, marshy coastal areas with soil rich in water but poor in oxygen. What special adaptation helps them obtain air?

  1. Stems that store water
  2. Breathing roots (pneumatophores) growing above the soil
  3. Broad leaves covered with thick wax
  4. Spines instead of leaves

Q10. Which component of food remains undigested in human digestive tract but adds bulk to stool and helps prevent constipation?

  1. Proteins
  2. Roughage (Dietary Fibre)
  3. Carbohydrates
  4. Fats

Q11. Plant-eating animals (herbivores) have well-developed ________ for biting, whereas flesh-eating animals (carnivores) have well-developed ________ for tearing flesh.

  1. Premolars, Canines
  2. Incisors, Canines
  3. Molars, Incisors
  4. Canines, Premolars

Q12. Why do we prefer to wear light-coloured or white cotton clothes during summer?

  1. They absorb heat and keep the body warm.
  2. They reflect solar heat and allow air circulation to keep the body cool.
  3. They trap air and prevent evaporation of sweat.
  4. They are waterproof and prevent moisture loss.

Q13. Select the correct statement regarding states of matter.

  1. Gases have a fixed shape but no fixed volume.
  2. Liquids have neither fixed shape nor fixed volume.
  3. Solids have a fixed shape and a fixed volume.
  4. Gases have higher density than solids.

Q14. Which organ of the human digestive system is the longest and is the main site for complete digestion and nutrient absorption?

  1. Stomach
  2. Large Intestine
  3. Small Intestine
  4. Oesophagus

Q15. The process of transformation of water vapour into liquid water droplets on cooling is termed as:

  1. Evaporation
  2. Condensation
  3. Melting
  4. Freezing

Q16. What causes sea breeze in coastal areas during daytime?

  1. Air over the land heats up faster and rises, replaced by cooler air blowing from the sea.
  2. Air over the sea heats up faster and rises, replaced by cooler air blowing from land.
  3. Land loses heat faster than the sea during daytime.
  4. High pressure builds over land and low pressure over sea.

Q17. Identify the insect that undergoes a 3-stage life cycle (Egg → Nymph → Adult):

  1. Butterfly
  2. Frog
  3. Cockroach
  4. Housefly

Q18. Which simple machine consists of a sloping surface used to raise heavy objects with less effort?

  1. Lever
  2. Inclined Plane
  3. Pulley
  4. Wedge

Q19. Which of the following diseases is caused by a virus?

  1. Typhoid
  2. Tuberculosis
  3. Dengue
  4. Cholera

Q20. What force causes an apple to fall down towards the ground from a tree branch?

  1. Frictional Force
  2. Gravitational Force
  3. Magnetic Force
  4. Electrostatic Force

Q21. Identify the odd one out based on the method of food preservation:

  1. Freezing
  2. Canning
  3. Dehydration (Drying)
  4. Boiling for immediate consumption

Q22. Birds like ducks and swans have webbed feet. This adaptation primarily helps them to:

  1. Perch firmly on tree branches
  2. Swim easily in water
  3. Tear flesh into small pieces
  4. Catch prey while flying

Q23. Which planet in our Solar System is known as the ‘Red Planet’?

  1. Venus
  2. Jupiter
  3. Mars
  4. Saturn

Q24. Pores present on the underside of plant leaves used for gas exchange are known as:

  1. Chlorophyll
  2. Stomata
  3. Veins
  4. Root hairs

Q25. Which natural fibre is obtained from the stem of a plant?

  1. Cotton
  2. Jute
  3. Wool
  4. Silk

Q26. Which part of a tooth contains blood vessels and nerves?

  1. Enamel
  2. Dentine
  3. Pulp
  4. Crown

Q27. When talcum powder is sprinkled on a carrom board, it reduces ________ to make strikers move smoothly.

  1. Gravity
  2. Friction
  3. Magnetism
  4. Air resistance

Q28. Soil erosion on riverbanks can be effectively minimized by:

  1. Deforestation
  2. Building embankments and afforestation
  3. Overgrazing
  4. Tilling land frequently

Q29. Bowl-shaped hollow depressions found on the surface of the Moon caused by meteorite impacts are called:

  1. Valleys
  2. Craters
  3. Mountains
  4. Basins

Q30. Which vitamin is synthesized by our body in the presence of sunlight and strengthens bones?

  1. Vitamin A
  2. Vitamin B
  3. Vitamin C
  4. Vitamin D

SECTION 3: ACHIEVERS SECTION

Q31. Study the following table showing states of three substances (P, Q, R) at different temperatures:
• Substance P: Solid at 10°C, Solid at 40°C, Liquid at 90°C
• Substance Q: Liquid at 10°C, Liquid at 40°C, Gaseous at 90°C
• Substance R: Liquid at 10°C, Gaseous at 40°C, Gaseous at 90°C
Which substance has the LOWEST boiling point and which has the HIGHEST melting point respectively?

  1. Lowest Boiling: R | Highest Melting: P
  2. Lowest Boiling: P | Highest Melting: Q
  3. Lowest Boiling: Q | Highest Melting: R
  4. Lowest Boiling: R | Highest Melting: Q

Q32. Refer to the given food web:
Plants → Grasshopper → Frog → Snake → Eagle
Plants → Rabbit → Snake
If the entire population of Snakes is completely eliminated due to an epidemic, what immediate effect will be observed?

  1. The population of Frogs will decrease while Grasshoppers increase.
  2. The population of Frogs and Rabbits will increase, leading to heavy grazing on Plants.
  3. The population of Eagles will immediately double.
  4. Plants will overgrow rapidly without control.

Q33. Sushil is pushing a heavy wooden box up an inclined wooden ramp into a delivery truck.
1. Chemical energy from food converts into Kinetic energy while moving.
2. At the top deck, energy is stored as Potential energy.
3. Some energy is lost as Heat due to friction between box and ramp.
Which of the following statements are TRUE regarding this setup?

  1. 1 and 2 only
  2. 2 and 3 only
  3. 1, 2, and 3
  4. 1 and 3 only

Q34. Four equal soil samples (Sandy, Clayey, Loamy, Gravel) were placed in funnels lined with filter paper, and 50 mL of water was poured over each. The volume of collected drained water in measuring cylinders below was recorded:
• Sample X collected 42 mL water
• Sample Y collected 12 mL water
• Sample Z collected 25 mL water
Identify soil samples X, Y, and Z respectively.

  1. X = Clayey, Y = Sandy, Z = Loamy
  2. X = Sandy, Y = Clayey, Z = Loamy
  3. X = Loamy, Y = Sandy, Z = Clayey
  4. X = Sandy, Y = Loamy, Z = Clayey

Q35. Read the statements about Earth and Moon solar movements:
Statement 1: The rotation of Earth on its tilted axis causes day and night.
Statement 2: The revolution of Earth around the Sun along with tilted axis causes seasons.
Statement 3: If Earth’s speed of rotation is halved, the duration of one day-night cycle will become 48 hours.
Select the correct option:

  1. Only Statement 1 is correct.
  2. Statements 1 and 2 are correct, Statement 3 is incorrect.
  3. All Statements 1, 2, and 3 are correct.
  4. Statements 2 and 3 are correct, Statement 1 is incorrect.

 

 

ANSWER KEYS & DETAILED EXPLANATIONS

Q1. Correct Answer: Option A
Explanation: TPMBS – Each letter is shifted by +1 position in the English alphabet (P→Q, L→M, A→B, N→O, T→U). Applying +1 to SOLAR: S→T, O→P, L→M, A→B, R→S, resulting in TPMBS.

Q2. Correct Answer: Option A
Explanation: East – Facing North, 3/4 turn right (270° clockwise) brings her facing West. From West, a 1/2 turn left (180° counter-clockwise) points her directly to East.

Q3. Correct Answer: Option B
Explanation: 64 – The pattern doubles the previous number sequentially: 4×2=8, 8×2=16, 16×2=32, 32×2=64, 64×2=128.

Q4. Correct Answer: Option C
Explanation: 4 – A closed square is a four-sided polygon, requiring exactly 4 straight line segments.

Q5. Correct Answer: Option D
Explanation: Mountain – River, Lake, and Pond are all natural water bodies, whereas a Mountain is a landform.

Q6. Correct Answer: Option D
Explanation: Oxygen – Plants absorb water from soil, carbon dioxide from air, and light from Sun to prepare food during photosynthesis. Oxygen is released as a byproduct.

Q7. Correct Answer: Option A
Explanation: Grass → Grasshopper → Frog → Snake – Grass (producer) is eaten by Grasshopper (primary consumer/herbivore), eaten by Frog (secondary consumer/carnivore), eaten by Snake (tertiary consumer).

Q8. Correct Answer: Option B
Explanation: Circulatory system – Consisting of heart, blood, and blood vessels, it distributes oxygen, nutrients, and removes metabolic waste.

Q9. Correct Answer: Option B
Explanation: Breathing roots (pneumatophores) – Swampy coastal soils lack air/oxygen; special aerial roots grow upwards above water surface to absorb atmospheric oxygen.

Q10. Correct Answer: Option B
Explanation: Roughage (Dietary Fibre) – Cannot be digested by human enzymes, but adds essential bulk to undigested food waste, facilitating smooth bowel movements.

Q11. Correct Answer: Option B
Explanation: Incisors, Canines – Herbivores possess sharp incisors for cutting/biting plant leaves, while carnivores possess long, pointed canines for tearing flesh.

Q12. Correct Answer: Option B
Explanation: Reflect solar heat and allow air circulation – Light colours reflect radiant solar heat rather than absorbing it, maintaining cooler body temperature.

Q13. Correct Answer: Option C
Explanation: Solids have fixed shape and volume – Solid particles are tightly packed in rigid arrangements giving definite geometry and volume.

Q14. Correct Answer: Option C
Explanation: Small Intestine – Measuring around 6 meters in length, it receives digestive enzymes from liver and pancreas where absorption occurs into blood capillaries.

Q15. Correct Answer: Option B
Explanation: Condensation – The phase change of water vapour (gas) turning into liquid droplets upon losing heat energy.

Q16. Correct Answer: Option A
Explanation: Land heats up faster than sea – During daytime, warm air above land expands and rises (low pressure), causing cool sea breeze to rush inland from water.

Q17. Correct Answer: Option C
Explanation: Cockroach – Cockroaches undergo incomplete metamorphosis with 3 life stages (Egg → Nymph → Adult). Butterflies and frogs have 4/complex stages.

Q18. Correct Answer: Option B
Explanation: Inclined Plane – A slant surface that reduces required input effort to raise heavy loads to a higher elevation over a longer distance.

Q19. Correct Answer: Option C
Explanation: Dengue – Caused by the Dengue virus transmitted by Aedes mosquitoes. Typhoid, Tuberculosis, and Cholera are caused by bacterial pathogens.

Q20. Correct Answer: Option B
Explanation: Gravitational Force – Earth’s attractive gravitational pull draws all objects with mass towards its centre.

Q21. Correct Answer: Option D
Explanation: Boiling for immediate consumption – Freezing, canning, and dehydration are long-term preservation techniques; boiling without airtight storage is temporary cooking.

Q22. Correct Answer: Option B
Explanation: Swim easily in water – Skin folds between toes create paddle-like surfaces that push against water efficiently.

Q23. Correct Answer: Option C
Explanation: Mars – Mars is rich in iron-oxide (rust) on its surface soil and atmosphere, giving it a characteristic reddish appearance.

Q24. Correct Answer: Option B
Explanation: Stomata – Microscopic openings present mostly on leaf undersides regulated by guard cells for intake of CO2 and release of O2 and water vapour.

Q25. Correct Answer: Option B
Explanation: Jute – Jute fibers are extracted from the stem of the Corchorus plant through retting. Cotton comes from fruit/seed, wool/silk from animals.

Q26. Correct Answer: Option C
Explanation: Pulp – The innermost soft tissue layer of tooth containing living nerves and blood vessels.

Q27. Correct Answer: Option B
Explanation: Friction – Powder smooths microscopic irregularities between carrom board surface and striker/coins, decreasing sliding resistance.

Q28. Correct Answer: Option B
Explanation: Building embankments and afforestation – Plant roots hold soil tightly together while embankments physically protect banks from rushing water currents.

Q29. Correct Answer: Option B
Explanation: Craters – Circular bowl-like pits formed when meteorites and asteroids impact the airless surface of the Moon.

Q30. Correct Answer: Option D
Explanation: Vitamin D – Produced in skin when exposed to ultraviolet solar rays; essential for calcium absorption and strong bones/teeth.

Q31. Correct Answer: Option A
Explanation: Lowest Boiling: R | Highest Melting: P – Substance R turns to gas at 40°C (lowest boiling point). Substance P remains solid up to 40°C and melts into liquid before 90°C (highest melting point).

Q32. Correct Answer: Option B
Explanation: Frogs and Rabbits increase – Without snakes (predator), the population of frogs and rabbits will grow rapidly due to lack of predation, increasing pressure on plant vegetation.

Q33. Correct Answer: Option C
Explanation: 1, 2, and 3 – Sushil uses metabolic chemical energy (Food → Kinetic), stores gravitational potential energy at height, and overcomes surface friction generating heat.

Q34. Correct Answer: Option B
Explanation: X = Sandy, Y = Clayey, Z = Loamy – Sandy soil has large particles/high percolation (retains least water, drains 42 mL). Clayey retains maximum water (drains 12 mL). Loamy has moderate retention (drains 25 mL).

Q35. Correct Answer: Option C
Explanation: All Statements 1, 2, and 3 are correct – Earth rotates on its axis every 24h (day/night); revolution + tilt creates seasons; halving rotational speed doubles day duration from 24h to 48h.

 

Updated: October 7, 2026 — 2:25 am

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