A. Protein powers the body.
C. Phobias are irrational fears about something. They are "irrational" because a person may fear something that would not logically pose any real threat or harm, such as fearing small spaces (claustrophobia) like elevators because one might feel like they are suffocating, even though elevators obviously do not cause people to suffocate.
You can keep them health by vitamins C,D,and K and calcium
The answer is not parasites, or pathogens. These are tested for before the donor and recipient are even matched
The antibody screen will test for antigens. So I believe the answer is Antibodies.