Retroviruses become proviruses integrated into the host chromosome soon after infecting the host cell, and can remain there indefinitely. The provirus DNA can then be transcribed and translated by the host cell, making new retroviral RNA genomes, enzymes, and structural proteins. New retroviral virions can then assemble and bud through the host cell membrane continuously over long periods of time. What is one implication of this retroviral life cycle?

Retroviruses become proviruses integrated into the host chromosome soon after infecting the host cell, and can remain there indefinitely. The provirus DNA can then be transcribed and translated by the host cell, making new retroviral RNA genomes, enzymes, and structural proteins. New retroviral virions can then assemble and bud through the host cell membrane continuously over long periods of time. What is one implication of this retroviral life cycle?

a) Because retroviruses have multiple enzymes (reverse transcriptase, protease, and integrase), they can rapidly kill the host cell once enough of these enzymes are synthesized by the host.

b) Once many new virus particles are produced, the host cell will lyse to release them.

c) Retroviruses have a typical one-step viral growth curve, which leads to the host being overwhelmed quickly.

d) It is difficult to completely cure an animal host of the virus, since anti-retroviral drugs will only eliminate circulating virions, not proviruses.

d) It is difficult to completely cure an animal host of the virus, since anti-retroviral drugs will only eliminate circulating virions, not proviruses.

Explanation:

When retroviruses integrate their genome into the host chromosome, it becomes difficult to cure them. This is due to the fact that the drugs used to cure the infection would target only virions present in the animal host. However, the presence of retroviral genome as provirus would lead to the formation of new virion progeny continuously. Therefore, killing the circulating virions does not eliminate the virus completely from the host body.

"a.) well–developed vascular system."

i think that is new experiments yield untrustworthy data and should be carefully considered, because you don't know what will happen with the experiments.