Final answer:
DAF, MCP, and CR1 are proteins that inhibit complement activation.
Step-by-step explanation:
DAF (Decay Accelerating Factor), MCP (Membrane Cofactor Protein), and CR1 (Complement Receptor 1) are all proteins that play a role in regulating the complement system, which is part of the immune response. These proteins help to prevent excessive complement activation and maintain a balance in the immune response.
For example, DAF inhibits the formation of membrane attack complex (MAC), which can damage healthy cells. MCP helps to degrade C3b (a component of the complement system) and prevent its deposition on host cells. CR1 helps in promoting the clearance of immune complexes.
Therefore, the correct answer is A) Inhibit complement activation.