Which of the following is a basic characteristic of a virus?

• A. It requires a host cell to replicate because it cannot reproduce independently.
• B. It contains ribosomes and generates ATP through its own metabolism.
• C. It is composed of a cell wall and plasma membrane surrounding cytoplasm.
• D. It is a unicellular organism that reproduces by binary fission.

Answer: (A)

Verified step by step guidance

1. Understand that viruses are unique infectious agents that differ fundamentally from cellular life forms such as bacteria and eukaryotic cells.
2. Recall that viruses lack cellular structures like ribosomes and do not have metabolic machinery to generate ATP or carry out independent metabolism.
3. Recognize that viruses do not have a cell wall, plasma membrane, or cytoplasm, which are typical features of cellular organisms.
4. Know that viruses cannot reproduce by binary fission or any form of independent cell division; instead, they must infect a host cell to replicate.
5. Conclude that the defining characteristic of viruses is their dependence on a host cell for replication, as they cannot reproduce independently.