When it is cold, the blood vessels of the skin

Explanation

When our bodies get cold, they need to regulate our internal temperature to keep us warm. One of the ways our body does this is by controlling the amount of blood that flows to our skin. The skin is the outer layer of our body and is in direct contact with the environment, so it's important that our body keeps it at the right temperature. The question is asking what happens to the blood vessels in our skin when we get cold. Option A says that the blood vessels dilate, which means they get wider to increase blood flow to the skin. However, this is not correct. Option B says that the blood vessels constrict, which means they get narrower to reduce the amount of blood flowing to the skin. This is the correct answer because if less blood flows to the skin, less heat is lost from the body. Option C says that the blood vessels dilate to reduce the amount of blood flowing to the skin, which is incorrect because dilating the blood vessels would actually increase blood flow. Option D says that the blood vessels constrict to increase the amount of blood flowing to the skin, which is also incorrect because constriction reduces blood flow. In summary, when it is cold, the blood vessels of the skin constrict to reduce the amount of blood flowing to the skin, helping to keep our bodies warm.