I think the answer to this question is two to three.
Development of tissue typing changed organ transplantation as
Tissue typing minimizes the chance of rejection
Explanation:
Before tissue typing the chances of rejection of organs y the body of the person needing a transplant was very high and it was a dangerous procedure with little chance of success.
Tissue typing is a process by which the sample tissue of the donor is matched with the sample tissue of the patient in need of help. This makes it viable for the person to know if the organs will be rejected or not before the actual surgery takes place and has allowed for greater successes in transplant thus.
The answer is true. They fight things like the flu, but they don't fight bacteria like antibiotics.
The answer is definitely A.