The complement fixation test uses red blood cells as the target for complement activation. Test serum containing antibodies is combined with a known amount of antigen in a tube, and then the RBCs and antibodies against the RBCs are added. A positive result for the complement fixation test would be
A) a line of precipitate near the bottom of the tube. B) a cloudy solution in the tube. C) loss of color in the tube. D) a fluorescent precipitate. E) a solution that is clear due to precipitation of RBCs.