Capillaries<span> are the smallest of the body's blood </span>vessels<span>. They are only one cell thick, and they are the sites of the transfer of oxygen and other nutrients from the bloodstream to other tissues in the body; they also collect carbon dioxide waste materials and fluids for return to the veins.</span>
I think it’s 90%. And it increases the risk of developing hypertension.
I think it's D. Because the students impulse is to do it because its cool, because all their friends do it. Hope my answer helps you! :)
