Hormones are chemical substances that help to regulate processes in the body. Hormones are secreted by glands and travel to their target organs in the bloodstream. Hormones can be used to control human fertility.
I think BO or B, but BO has more chance.
The difference between an artery and a vein is that arteries are larger, more muscular and more elastic than veins; they carry blood that is under pressure from having been pumped out of the heart; veins are under much less pressure, so they are not as strong
To answer specific questions about the natural world
