In mammals, body temperature is controlled by a structure in the brain called the hypothalamus. The hypothalamus is able to sense even slight variations in body temperature. This structure is responsible for bodily responses that include thirst, the activation of sweat glands, and the dilation of blood vessels near the skin. Each of these mechanisms works to restore body temperature to a normal range.

Based on this information, in which of the following scenarios would the hypothalamus initiate steps to reduce body temperature in a mammal?

Answer options:
-when any increase in body temperature is sensed.
-when body temperature rises above a set point.
-when body temperature exceeds external temperatures.
-every six to eight hours when the animal is awake.