1) E

Homeostatsis (temperature, water level in body etc.) is related to the hypothalamus. This rules out A,B and C.

When our temperature rises, the hair muscles relax, meaning our hair (on hands) lay flat. This rules out F.

Our arterioles dilate (become wider or larger) to create a larger surface area. This allows more heat to be radiated out of our body. This rules out option D.

Hence E is correct.