Natural Science CLEP Prep Practice Exam

Nitrogen is the most abundant chemical element in the atmosphere, making up approximately 78% of the air we breathe. While carbon, hydrogen, and oxygen are also present in the atmosphere, they are not as abundant as nitrogen. Carbon and oxygen are essential for life and are present in the form of carbon dioxide, while hydrogen is mostly found in the form of water vapor. However, their concentrations in the atmosphere are much lower compared to nitrogen. Therefore, options A, B, and C are incorrect.