What two things are necessary to prove an exposure occurred?

Mario was conducting research regarding the treatment of aids victims using stem cells. he found a source that was written recently and the author was known. unfortunately, he could not determine if it had been peer reviewed.

Viruses use the host's machinery to make copies of themselves. however, some human viruses require a type of replication that humans do not normally have. for example, humans normally do not have the ability to convert rna into dna. how can these types of viruses infect humans, when human cells cannot perform a particular role that the virus requires? a) the virus causes mutations in the human cells, resulting in the formation of new enzymes that are capable of performing these roles.b) the viral genome codes for specialized enzymes not in the host.c) the virus infects only those cells and species that can perform all the replication roles necessary.d) viruses can stay in a quiescent state until the host cell evolves this ability.

An electric shock can result in anything from a slight tingling sensation to immediate cardiac arrest. the severity depends on the amount of current flowing through the body, the current's path through the body, the length of time the body remains in the circuit, and the current's