SAT Subject Biology Practice Question 374: Answer and Explanation
4. Important thermoregulatory structure in humans
D. Guard cell
E. Sweat gland
Correct Answer: E
E As always, eliminate first. Choices C and D are not found in humans and can be eliminated. A thermoregulatory structure is one that helps control temperature. The epidermis (choice B) prevents loss of water, but does not really aid in thermoregulation (that's the job of the dermis), so eliminate choice B as well. You may be tempted by choice A, because hair plays a minor thermoregulatory role in humans (its role is much more important in other animals), but a sweat gland is a major thermoregulatory structure.