Air around us

How much percentage of nitrogen is present in the air?

• 21%

• 4%

• 78%

• 33%

Which of these causes air pollution?

• Throwing litter here and there

• Smoke from factories

• Both of these

• None of these

_________ is the process by which oxygen reacts with a fuel and releases heat energy

• Respiration

• Oxygen cycle

• None of these

• Combustion

Moving air is called?

(a)  

A layer of air called __________ surrounds the earth.

• Stratosphere

• Troposphere

• Atmosphere

(a)   is needed for respiration by living things

Water is present in the air in the form of ____________

• Water vapor

• Water cycle

• Carbon-dioxide

• Oxygen

The amount of water vapour present in the air is referred as humidity

• True

• False

Is carbon dioxide important for only animals?

• Yes

• No

A __________ is an instrument used to show the direction of the wind.

• Pin wheel

• Wind mill

• Wind vane

• Fan