Question

what greenhouse gas is the main pollutant that is warming earth?
a. carbon dioxide
b. oxygen
c. hydrogen sulfide
d. nitrogen

Explanation:

Greenhouse gases trap heat in the Earth's atmosphere. Carbon dioxide ($CO_2$) is a major greenhouse gas. Human activities like burning fossil fuels release large amounts of $CO_2$. Oxygen ($O_2$) is essential for respiration but not a greenhouse gas. Hydrogen sulfide ($H_2S$) is a toxic gas with a rotten - egg smell and not a main greenhouse gas. Nitrogen ($N_2$) makes up most of the Earth's atmosphere but is not a greenhouse gas.

Answer:

A. carbon dioxide