Answer:
blood transfusion cancer cells killed radiation therapy → bone marrow grows
Explanation:
The correct answer is A) microorganisms are transmitted from one organism to another.
The chain of infection is a process in which microorganisms are transmitted from one organism to another.
The chain of infection starts with the agent of infection that is the one which makes people sick. It exists in a reservoir, where the agent of infection lives. There is a portal of exit. It is the way the agent leaves the reservoir. Then we have the mode of transition. It could indirect or direct contact with the agent. The agent o infection enters a new body through what is known as a portal on entry. Finally, the host. It is the individual who receives this agent and gets sick.
