Chọn đáp án đúng nhất

They/ not answer/ phone/ this morning/ so/ must/ out/.

A. They hasn’t answered the phone this morning so they must have been out.

B. They didn’t answer the phone this morning so they must be out.

C. They didn’t answer the phone this morning so they must have gone out.

D. They hasn’t answered the phone this morning so they must go out.