Answer
A
Work Step by Step
The alternative complement activation pathway involves factors B, D, and P. Antibodies' bonds to antigens are necessary for the classical activation of complement, whereas activation of the alternative pathway occurs independently of antibodies. The alternative pathways are the cleavage of C3 into C3a and C3b. Another plasma protein, factor D, cleaves factor B. This enzyme is stabilized by a third protein--factor P.
