Final answer:
The statement is true; viruses can have nucleic acids that are single or double stranded, and these can be either DNA or RNA, leading to considerable diversity in their genetic makeup. The correct option is A.
Step-by-step explanation:
True: Viral nucleic acid may be single-stranded or double-stranded DNA or RNA. Viral genomes are highly variable and can be composed of DNA or RNA, which exists in either single-stranded or double-stranded forms. This adaptation allows viruses to use different methods of replication and transcription, depending on their environment and life cycle.
For example, the influenza virus has a single-stranded RNA genome with negative polarity, while rotaviruses contain double-stranded RNA. Additionally, viral DNA can be replicated through an RNA intermediate, with the RNA serving directly as mRNA or as a template to create mRNA.
The presence of these diverse genetic structures makes virus classification complex, which is exemplified in the Baltimore classification scheme.