Similar to other vertebrate animals, humans possess retroviruses that exist in two forms: as normal genetic elements in their chromosomal DNA (endogenous retroviruses) and as horizontally-transmitted infectious RNA-containing viruses which are transmitted from human-to-human (exogenous retroviruses, e. g. HIV and human T cell leukemia virus, HTLV). Endogenous retroviruses in animals and humans probably evolved from transposable elements, some of them gaining the ability to package themselves in a virion structure, leave the cell and infect another cell.

True

Explanation:

Retrovirus is a virus containing an RNA as a genetic material which infects the host cell by integrating its RNA into the genome of the host cell.

The retrovirus uses their reverse transcriptase enzyme to synthesise DNA from the RNA and then insert the DNA into a host DNA.

The studies on the genome of the human have shown that about 5-8% of the human genome is comprised of these retrovirus called endogenous retroviruses which act as transposable elements and some retroviruses use humans as the host to replicate and vector to transfer from human to a human called exogenous retroviruses.

Thus, true is the correct answer.