Once activated, the complement cascade is an ordered process. Each reaction leads to another reaction. This activity asks you to place the cascade reactions in the order they occur, starting with the C1.
A. C1 cleaves C2 and C4
B. C2a and combine to form an enzyme
C. C1 interacts with antibody that is bound to pathogen.
D. C3 is split into C3a and C3b

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.

Mitochondria is the cell organelle that produced the energy that is needed in the body system in form of atp, that is why it is called the power house of the cell. energy is needed by the living organisms to carry out the activities which sustain life.  if the mitochondria is destroyed atp will not be produced. if the mitochondria is destroyed, energy production will stop and the affected living organism will not have the energy to carry out the necessary life processes; this will lead to the death of the organism.