A Patient Is Suffering from a Condition Requiring Multiple Blood

A patient is suffering from a condition requiring multiple blood transfusions. They have type A blood and their first transfusion was perfectly successful. However, their second transfusion of type A blood causes them to become very ill and observation of their blood reveals agglutination. What has happened to cause their second transfusion to fail?

A) The blood used in the first transfusion contained Rh antigens, which caused the patient to produce anti-Rh antibodies and attack the blood from the second transfusion.
B) They have developed a sensitivity to A antigens after being exposed to the first transfusion.
C) The second transfusion must have had anti-A antibodies, which began attacking their blood.
D) The blood used in the second transfusion must have come from a pregnant woman with Rh-negative blood.