UPSC Civil Services 2016 Prelims General Studies Paper I

(i) A virus is a small infectious agent that replicates only inside the living cells of other organisms. Viruses can infect all types of life forms, from animals and plants to microorganisms, including bacteria and fungi.
(ii) According to the type of the host they infect, viruses are classified mainly into the following four types:
(a) Plant viruses including algal viruses-RNA/ DNA
(b) Animal viruses including human virusesDNA/RNA
(c) Fungal viruses(Mycoviruses)-ds RNA
(d) Bacterial viruses (Bacteriophages) including cyanophages-DN
Hence answer "(d)".