Final answer:
The genome of retroviruses is composed of single-stranded RNA (ssRNA). Using the enzyme reverse transcriptase, retroviruses convert ssRNA into DNA to integrate into the host's genome as a provirus, establishing chronic infection.
Step-by-step explanation:
The genome of retroviruses is made of C) ssRNA. Retroviruses, such as HIV, carry their genetic information in the form of single-stranded RNA. Upon infecting a host cell, retroviruses use an enzyme known as reverse transcriptase to convert their ssRNA into complementary DNA (cDNA). This cDNA is then made into double-stranded DNA (dsDNA) and integrated into the host cell's genome, where it is referred to as a provirus. This provirus becomes a permanent part of the host's DNA, enabling the virus to establish a chronic infection and produce viral proteins by utilizing the host's cellular machinery.