Thermoregulation Through Shivering

Steps:

• Identify period 1 as initial body temperature rise due to cold exposure triggering heat production.
• Recognize period 2 as further temperature increase from intensified heat generation mechanism.
• Link rises to involuntary muscle activity that converts chemical energy to thermal energy.
• Confirm mechanism matches physiological response to hypothermia without external factors.

Why C is correct:

• Shivering produces heat via rapid muscle contractions, raising core temperature as per homeostatic thermoregulation principles.

Why the others are wrong:

• A: Reduced air temperature cools the body; increased air temperature would prevent rises.
• B: Vigorous exercise raises temperature, but sweating cools it, not sustaining increases.
• D: Vigorous exercise elevates temperature initially, but shivering alone explains both periods without exercise.

Final answer: C