An accident victim receives a blood transfusion. Shortly thereafter, he begins to have difficulty breathing, develops a fever, and experiences nausea and vomiting. Which of the following is the most likely interpretation of these events?

A) the blood transfusion was mismatched.
B) the blood transfusion contained pyrogens.
C) the recipient had previously been exposed to foreign blood group antigens.
D) the blood transfusion was mismatched and contained pyrogens.
E) the blood transfusion was mismatched and the recipient had previously been exposed to the foreign blood group antigens.