When You Go Outside on a Hot Summer Day,your Body

When you go outside on a hot summer day,your body temperature heats up above the normal range.Receptors in your brain detect the change in body temperature.The brain activates nerve cells that send messages to sweat glands,causing the body temperature to fall as the sweat evaporates from the skin.What part of this feedback loop is the stimulus?

A) nerve cells
B) increased body temperature
C) sweat glands
D) brain