Final answer:
The correct option is c. DAF cleaves and inactivates the C3 convertase on the surface of a human cell, while MCP stabilizes the C3 convertase on the surface of a pathogen.
Step-by-step explanation:
DAF (Decay Accelerating Factor) and MCP (Membrane Cofactor Protein) are two proteins involved in the complement system, which is a part of the immune response. The complement system helps to identify and eliminate pathogens from the body.
Option C is true regarding DAF and MCP. DAF cleaves and inactivates the C3 convertase enzyme on the surface of a human cell, preventing excessive complement activation and damage to host cells. MCP stabilizes the C3 convertase on the surface of a pathogen, promoting the efficient activation of the complement system against the pathogen.