Q1 of 75 Page 441

Write true or false for the following statements :

Oxygen is returned to the atmosphere in only one major process, that is, respiration.

False

Photosynthesis is the major process by which oxygen is returned to the atmosphere. During the process of respiration carbon di oxide is being released into atmosphere.


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39

When we breathe in air, nitrogen also goes inside along with oxygen. What is the fate of this nitrogen?

 40

Smog is a combination of:

 2

Write true or false for the following statements :

The process of nitrogen-fixing is done by bacteria in the presence of oxygen.

 3

Write true or false for the following statements :

Oxygen is necessary to life for most of the organisms in the process of respiration but some forms of life, especially bacteria, are poisoned by elemental oxygen.