Question

a scientist is examining the role of an element found in fats and carbohydrates of living things. this element makes up 65% of human body mass. which statement describes the element he is studying? he is studying oxygen, which can also be found in proteins. he is studying oxygen, which is the most abundant element in the atmosphere. he is studying nitrogen, which can also be found in proteins. he is studying nitrogen, which is the most abundant element in the atmosphere.

Explanation:

• Oxygen in the body: Oxygen makes up about 65% of human body mass. It is found in fats (e.g., triglycerides: \(C_{55}H_{98}O_{6}\)), carbohydrates (e.g., glucose: \(C_{6}H_{12}O_{6}\)), and proteins (e.g., the general formula of an amino - acid: \(R - CH(NH_{2})COOH\) has oxygen in the carboxyl group).
• Nitrogen in the body: Nitrogen is not the most abundant element in the human body by mass. While it is present in proteins (in the amino group \( - NH_{2}\)), it does not account for 65% of body mass.
• Oxygen vs nitrogen in the atmosphere: Nitrogen (\(N_{2}\)) is the most abundant element in the atmosphere (about 78%), not oxygen (about 21%).

Answer:

He is studying oxygen, which can also be found in proteins.