He said to interviewer, "Could you please repeat the question?"

Answer: Option C

In direct and indirect speech, when we report someone's request, we often use the verb "requested" followed by an indirect request. The structure of indirect speech for requests is typically: "requested + [indirect request]."

In this case, the original sentence is a polite request: "Could you please repeat the question?"

The correct indirect speech transformation is: "He requested the interviewer to repeat the question."

Therefore, the correct answer is Option C: He requested the interviewer to repeat the question. This option accurately conveys the original request in indirect speech without unnecessary additions or alterations.