If `CO_(2)` is absent in the atmosphere of earth, then

Earth Atmosphere

The CO_2 content in the atmosphere is

Which gas was absent in the atmosphere of primitive earth ?

The atmosphere of primitive earth was

Which gas was absent in the atmosphere of primitive earth?

Assertion: CO_(2) present in the atmosphere absorbs heat radiated from heat radiated from earth in the form of IR radiations. Reason: CO_(2) is a pollutant.

The source of CO_(2) in the atmosphere is