_____ is the element that makes up the largest percentage by mass in the human body.

_____ is the element that makes up the largest percentage by mass in the human body.

• A. Carbon
• B. Hydrogen
• C. Oxygen
• D. Nitrogen

Answer: (C)

Oxygen is the element that makes up the largest percentage by mass in the human body. This happens because most of the body’s mass comes from water, and each water molecule contains one oxygen atom. Water accounts for a large portion of body weight, and since oxygen also forms a big part of the mass of many organic molecules (like carbohydrates, fats, and proteins), it ends up contributing the most mass overall. In rough terms, oxygen makes up about two-thirds of body mass, while carbon, hydrogen, and nitrogen make smaller contributions. Hydrogen is light, so even though there are many hydrogen atoms, their mass is spread out, and the same goes for carbon and nitrogen where their overall mass contribution is less than that of oxygen.

Oxygen is the element that makes up the largest percentage by mass in the human body. This happens because most of the body’s mass comes from water, and each water molecule contains one oxygen atom. Water accounts for a large portion of body weight, and since oxygen also forms a big part of the mass of many organic molecules (like carbohydrates, fats, and proteins), it ends up contributing the most mass overall. In rough terms, oxygen makes up about two-thirds of body mass, while carbon, hydrogen, and nitrogen make smaller contributions. Hydrogen is light, so even though there are many hydrogen atoms, their mass is spread out, and the same goes for carbon and nitrogen where their overall mass contribution is less than that of oxygen.