The correct option is (b) single stranded RNA.
Explanation:
AIDS (Acquired Immunodeficiency Syndrome) was first reported in USA in 1981. It is caused by HIV (Human Immunodeficiency Virus). HIV is the member of retroviruses.
Later are so named because they contain an enzyme reverse transcriptase, which mediates the formation of DNA from RNA. The genetic material of HIV is single stranded RNA (ssRNA).