The Human Immune System Consists of

Multiple Choice

The human immune system consists of

A) about 10,000 cells that increase rapidly to trillions when an infection takes hold.
B) the heart and blood vessels and the blood cells within the vessels.
C) about 2 trillion cells, their secretions, and the organs where they are produced and stored.
D) all of the bacteria and viruses that are normally present in our bodies plus our blood cells.
E) the thyroid and thymus glands and their cells and secretions.