Carbon dioxide and water vapor are variable gases because .

their amounts vary throughout the atmosphere

Explanation:

There is very little that travels over the atmosphere

Vary=very little

Carbon dioxide and water vapor are variable gases because their amounts vary throughout the atmosphere.

Variable gases are not constant gases.  Constant gases have almost uniform concentrations through out the Earth's atmosphere.

i believe it is c.) 1575 j.

c. 75.7

i think that is the right