This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: General, Subject name: Microbiology
A nonspore-forming, gram-positive bacillus was isolated from a throat specimen from a primary school-aged child who had not been vaccinated with the DTaP vaccine. The strain isolated carried a bacteriophage on which the gene for toxin was encoded. How did this strain become toxigenic? 
Select and explain. 
A. Conjugation, B. Frameshift mutation, C. Homologous recombination, D. Transduction
D: Transduction
Answer: D: Transduction 
Explanation: Transduction (d) is the transfer of DNA mediated by bacteriophages. In generalized transduction, the phage virus can carry any segment of the donor chromosome; in specialized transduction, the phage carries only specific genes, generally those immediately adjacent to the site of prophage insertion.