The layer of air which surrounds the earth is:

Fish derive oxygen from:

During photosynthesis, plants take in 

Air is a mixture of

Which gas in the atmosphere is essential for respiration

Earthworm takes oxygen from the soil through:

The rate of photosynthesis is very high during:

Air is a type of:

Oxygen and carbon dioxide are replaced in nature through:

CNG means:

The amount of water vapour in the air at any place and time is:

Which of the following gases protects us from ultraviolet rays?

Which of these is not an organ for taking in oxygen?

Which of these is not true for combustion?

The presence of which component in air varies from place to place?

Which of the following statements is incorrect?

Wind does not help in the movement of which of the following?

What is not true about air?

Mountaineers carry oxygen cylinders with them because

Boojho took an empty plastic bottle, turned it upside down and dipped its open mouth into a bucket filled with water. He then tilted the bottle slightly and made the following observations:
(i) Bubbles of air came out from the bottle.
(ii) Some water entered into the bottle.
(iii) Nitrogen gas came out in the form of bubbles and oxygen gas dissolved in water
(iv) No bubbles formed, only water entered into the bottle 
which observation(s) is/are correct? 

Which of the following components of air is present in the largest amount in the atmosphere?

The components of air which are harmful to living beings are _______

Usha took a lump of dry soil in a glass and added water to it till it was completely immersed. She observed bubbles coming out. The bubbles cointain 

About one fifth of ordinary air is

Nitrogen is needed by the plants to make