Taking into account, three isotopes of hydrogen and three isotopes of oxygen occurring in nature, how many different kinds of water molecules can we expect on the Earth?

• Six

• Nine

• Twelve

• Eighteen

Which of the following changes when a particle is moving with uniform velocity?

• Speed

• Acceleration

• Velocity

• Position

Rocket works on the principle of conservation of

• mass

• energy

• momentum

• None of these

Wisdom teeth normally grow during the age of

• 12-15 yr

• 17-30 yr

• 34-40 yr

• 40-45 yr

Life of RBC in human blood is

• 30 days

• 60 days

• 120 days

• 15 h

156.

During day time, plants absorb

• O₂

• CO₂

• N₂

• CO

Nitrous oxide is called

• laughing gas

• tear gas

• producer gas

• methane gas

Force can be defined on the basis of

• Newton's second law of motion

• Newton's first law of motion

• Newton's third law of motion

• Newton's law of gravitation

Slope of the velocity-time graph gives the

• distance covered by a moving body

• velocity of a moving body

• acceleration of a moving body

• None of the above

Which of the following animals has the longest life span?

• Elephant

• Crocodile

• Dog

• Tortoise