An experiment showed that, on average, cell phones have 18 times the number of infectious agents as a toilet handle. in the chain of infection, the cell phone would represent a

The cell phone represents the reservoir.

Explanation:

An infection is the entry and multiplication of an infectious agent in the tissues of a host. Initially, the infectious agent penetrates the host body and there is proliferation (multiplication of microorganisms), with the consequent presentation of signs and symptoms, or not.

The infection happens through a chain of events called the transmission chain, that is, the infection develops within a cycle that depends on the presence of all the following elements:

In this case, we can say that in this cycle, the cell mentioned in the question above represents the reservoir, poles is the place where the infectious agent is deposited and can develop until it is ready to contact the host.

i agree d is most definitely correct!