Almost 99% of Earth's atmosphere is made up of two gases. What are the two gases and the percents of each? A) 21% oxygen and 78% nitrogen B) 21% water vapor and 78% oxygen C) 21% nitrogen and 78% oxygen D) 21% carbon dioxide and 78% oxygen

A should be the answer. 21% oxygen and 78% nitrogen

Explanation:

step 1: nitrogen fixation- conversion of atmospheric no₂ into forms useful to plants by lightning, bacteria, and cyanobacteria.

step 2: nitrification-process of converting ammonia to nitrite or nitrate.

step 3: assimilation-plant roots absorb new form of nitrogen.

step 4: ammonification-conversion of organic nitrogen to ammonia by bacteria involved in decomposition.

step 5: denitrification-bacteria turns the decomposed matter back into n₂o, which is released into atmosphere; repeat cycle.