What is the element that makes up 78% of the atmosphere?

The Earth is surrounded by air all around. Air is a very crucial element of our environment. The composition of air is majority is made up of nitrogen followed by oxygen and other gases. 

Air is composed of 78% of nitrogen, followed by oxygen(about 21% ), and other gases which are present in trace amounts in the air around us that as argon (about 0.9% ), carbon dioxide (about 0.04% ), and various other different gases. 

All gases in the air have their uses and benefit mankind in one or the other way as Oxygen is utilized by most living organisms for respiration without which living forms would not have existed. 

Nitrogen is fixed by microbes which is the source of fertilizer. The air protects mankind from the direct rays of the sun which are UV rays that cause several diseases like cancer, skin diseases, etc.

Hence nitrogen makes up most part of the air. The composition varies as we move more up from the earth's crust with no air in space. So, the composition of nitrogen varies from 73 to 78 percent. 

Hence, option B is correct.