Which Is True of the Biphasic Hemolysin Usually Associated with Paroxysmal

Which is true of the biphasic hemolysin usually associated with paroxysmal cold hemoglobinuria (PCH) ?

A) Anti-P that binds to red blood cells at body temperature but activates complement at cool temperatures
B) Anti-P that binds to red blood cells at cool temperatures but activates complement at body temperature
C) Anti-P1 that binds to red blood cells at body temperature but activates complement at cool temperatures
D) Anti-P1 that binds to red blood cells at cool temperatures but activates complement at body temperature