What effect would constriction of the blood vessels have in the body

higher blood pressure

Explanation:

when the vessels constrict they get smaller therefore in order for the blood to be pumped through the body the heart would have to work harder resulting in a higher blood pressure

increased blood pressure resulting in risk of heart attack

i'm thinking (a) to keep sand in place; ////////////

explanation: a sand fence or sandbreak, like a snow fence, is used to force windblown, drifting sand to accumulate in a desired place. sand fences are employed to control erosion, sand dune stabilization, keep sand off roadways, and to recruit new material in desert areas.