Question

An organ, such as a kidney, used for transplant needs to be tested for compatibility with the person who is to receive the organ. If this is not done, the (1) donated organ might attack the body (2) donated organ might attack the immune system (3) immune system might attack its own body cells (4) immune system might attack the donated organ

Answer 1

I believe it's number 4 because similar to when wrong blood types are transfused into a body, the immune system will see the donated organ as a foreign object and attack it to protect the organism (human).