Answer:
A. Blood vessels in the skin narrow and contract.
Step-by-step explanation:
If we will step outside without a coat on a snowy day then our blood vessels in the skin will become narrow and contract. It is a mechanism to conserve heat within our body in cold weather. If the blood vessels in the skin will become narrow and contract then less blood will flow in the blood vessels, this phenomenon is known as vasoconstriction. The blood of our body is warm but the exposure to the cold weather will cause the heat of the blood to dissipate into the environment. But constricted blood vessels will have less blood and hence heat loss is minimized which keeps the internal temperature of the body as normal even if outside environment is cold.