Question

fill in the blank with the best word to complete the sentence. the system is a group of proteins in the blood that attack pathogens that enter the body and kill them. done

Explanation:

The complement system is a part of the immune system. It consists of a group of proteins in the blood. When pathogens (like bacteria, viruses) enter the body, these complement proteins can be activated. They can directly attack the pathogens (for example, by creating holes in the pathogen's cell membrane) and also help other immune cells (like phagocytes) to recognize and destroy the pathogens better.

Answer:

complement