Question

carbon molecules make up about 18 percent of which of these?
choose one option
a complex carbohydrates
b human body mass
c omega-3 fatty acids
d earth’s crust

Explanation:

To solve this, we analyze each option:

• Option A: Complex carbohydrates have a higher carbon content (e.g., general formula \(C_n(H_2O)_m\) with significant carbon, but not ~18%).
• Option B: The human body is composed of various elements. Carbon makes up approximately 18% of human body mass (by mass, major elements: O~65%, C~18%, H~10%, etc.).
• Option C: Omega - 3 fatty acids are lipids; their carbon content is part of their structure but not around 18% (lipids have high C/H, but body mass percentage of C in fatty acids isn't 18% overall).
• Option D: Earth’s crust has very little carbon (mostly O, Si, Al, Fe, etc.), far less than 18%.

Answer:

B. Human body mass