The correct answer is B. You asked me why I was talking so much.
The sentence “You said to me, ‘Why are you talking so much?'” is in the past tense. This means that the speaker is referring to an event that happened in the past. In this case, the speaker is asking the listener why they are talking so much.
The answer A is incorrect because the speaker is asking the listener why they are talking so much, not why someone else is talking so much.
The answer C is incorrect because the speaker is asking the listener why they are talking so much, not why they were talking so much.
The answer D is incorrect because the speaker is asking the listener why they are talking so much, not why they had been talking so much.