Which of the following statements about viruses is true?

• A. Viruses can replicate independently without a host cell.
• B. Viruses are obligate intracellular parasites that require a host cell for replication.
• C. Viruses are classified as living organisms because they carry out metabolic processes.
• D. Viruses contain both DNA and RNA in their genetic material.

Answer: (B)

Verified step by step guidance

1. Understand the nature of viruses: Viruses are unique infectious agents that cannot carry out metabolic processes or reproduce on their own.
2. Recall the definition of obligate intracellular parasites: These are organisms that must live and reproduce inside the cells of a host organism.
3. Analyze the statement 'Viruses can replicate independently without a host cell': This is false because viruses lack the cellular machinery needed for replication and must hijack a host cell's machinery.
4. Consider the classification of viruses as living or non-living: Viruses are generally not classified as living organisms because they do not perform metabolic activities independently.
5. Evaluate the genetic material of viruses: Viruses contain either DNA or RNA, but never both simultaneously, which distinguishes them from cellular organisms.