A patient's serum is tested using the complement fixation test. If hemolysis occurs, __________.
A. it can be concluded that the patient had antibody to sheep red blood cells
B. complement was not fixed by antibodies in the patient's serum and was available to the antibodies, thus inducing lysis of sheep red blood cells
C. it can be concluded that the patient had antibody to the test antigen
D. complement bound to neither the antibody directed against the target antigen nor to the antibody directed against sheep red blood cells
E. the patient suffers from a disease in which complement is lacking or in low concentration