Answer:
C-A-B-D
Explanation:
The complement system: complement cascade is an ordered process is which every step occur in a orderly fashion; first
1) C1 interacts with an antibody that antibody is bound to a pathogen
and after it
2) C1 cleaves C2 and C4
, after it
3) C2a component and C4b both combine to form an enzyme,
after that
4) C3 is split into i) C3a and ii) C3b component
In complement system one sub-unit is large and other one is small.