"Who's the conductor of this bus?" he said, and paused for a reply.
A. He said who the conductor of that bus was and paused for a reply.
B. He asked who was the conductor of that bus and paused for a reply.
C. He asked whether who the conductor of that bus was and paused for a reply.
D. He asked who the conductor of that bus was and paused for a reply.
Answer: Option B

The direct question is the present simple of 'be'. We make the question form of the present simple of be by inverting (changing the position of)the subject and verb. So, we need to change them back before putting the verb into the past simple.
So the answer should be D
Wrong answer option A is correct
Wrong answer