I have no idea whether he has sisters, and if he does, _____？ [ ] A. how many sisters does he have

I have no idea whether he has sisters, and if he does, _____？ [ ] A. how many sisters does he have B. he has how many sisters C. how many he has sisters D. how many sisters he has

The correct choice is:

D. how many sisters he has

Here's why:

The sentence structure follows indirect (embedded) question rules: after "and if he does, …" we need subject + verb word order, not question word order.

Option A uses question word order (does he have), which is incorrect in this context.

Option B is not a standard structure for an indirect question.

Option C incorrectly places "he has sisters" instead of "he has" after how many.

Option D correctly uses "how many sisters he has", which fits the indirect question pattern.

So the completed sentence is:

I have no idea whether he has sisters, and if he does, how many sisters he has?

Even though it ends with a question mark because of the initial “I have no idea…”, the embedded clause keeps statement word order.