You have finished teaching a class on cold emergencies and want to assess if the class understands the concepts. You ask a student to discuss the regulation of temperature in the human body. You know that she understands when she makes which of the following statements?

a. "If the body becomes too hot or too cold, the brain sends instructions so that the body either retains or loses heat."
b. "If the air outside the body is cold and the body is too hot, the cold air will move into the body to cool it."
c. "Because cellular activity constantly generates heat, the body must always be cooler than the air that surrounds it."
d. "For its cells to function properly, the body must always be warmer than the air that surrounds it."

Answer: a