Explanation
All three statements use the absolute qualifier
“no virus” — and in each case, well-established exceptions exist, making all three statements incorrect.
Statement I is incorrect. Oceans are among the most virus-rich environments on Earth, estimated to contain more than 10³⁰ viruses. The vast majority are
bacteriophages that infect marine bacteria. Marine viruses like cyanophages infect phytoplankton such as Prochlorococcus and Synechococcus, playing a critical role in nutrient cycling, carbon cycling, and regulation of microbial populations.
Statement II is incorrect. A well-known class of viruses called bacteriophages (phages) specifically infects bacteria. They are considered the most abundant biological entities on Earth, found in soil, freshwater, marine water, and the human gut. The T4 bacteriophage, which infects E. coli, is a classic example. Bacteriophages are also being explored in phage therapy as an alternative to antibiotics against drug-resistant bacteria.
Statement III is incorrect. Viruses are obligate intracellular parasites — they depend entirely on host cell machinery to replicate. To facilitate this, many viruses actively manipulate the host cell’s transcriptional activity. For example, the HIV Tat protein enhances transcription of viral RNA, while the Herpes simplex virus suppresses host transcription to prioritise viral gene expression. Viruses can activate or repress host genes, hijack transcription factors, or introduce their own transcriptional machinery.
Since all three statements are factually incorrect, the answer is None.
UPSC Insight
The repeated use of “no virus” in all three statements is a deliberate trap. In biology-based questions, absolute terms like “no,” “all,” “always,” and “never” are almost always incorrect — a single exception is enough to invalidate the statement. Train yourself to be immediately suspicious of such language in UPSC options.