Bacteria can pick up new DNA in a few distinct ways, and each option here names one of those routes or a completely unrelated process. The key clue in the question is that a virus is doing the carrying.
- Transduction: A bacteriophage acts as an accidental delivery vehicle, packaging a fragment of one bacterium's DNA and dropping it off inside the next bacterium it infects, which fits a virus carrying host DNA perfectly.
- Integration: Describes the phage's own DNA settling into the host chromosome, not host DNA being carried anywhere, so the direction of transfer is wrong for this question.
- Transformation: Bacteria absorb loose DNA fragments straight from their environment, with no phage or virus acting as a courier at any point.
- Transcription: A routine step of making RNA off a DNA template inside a single cell, unrelated to any DNA moving between cells at all.
Since the question specifically calls out a virus as the carrier of host DNA between cells, that points to transduction rather than any of the other three processes. The correct answer is Transduction.