People warned us not to go out alone29/30People warned us not to go out alone.We were warned not going out alone.We were warned not to go out alone by people.We weren't warned to go out alone.We were warned not to go out alone.Giải thíchChọn đáp án D Giải thích : cấu trúc warn sb to V = be warned not to V: cảnh báo ai khỏi việc làm gì