For protection from the outside elements & harmful insects I would assume. Unless that's already obvious & they wanted a more in-depth answer.
D. Shows how water molecules attract to the glass tube.
One cardiac cycle is .8 seconds. A complete heartbeat is produced in one cardiac cycle. <span>The period of time that begins with contraction of the atria and ends with ventricular relaxation is known as the cardiac cycle. The period of contraction that the heart undergoes while it pumps blood into circulation is called systole.</span>
B. Cytoplasm- is made up of a jelly-like substance composed of mainly water and found between the cell membrane and nucleus. The cytoplasm makes up most of the body cells which hold organelles as well.
