ExercisesContentsDownloadsUNIT 20: PAST MODAL VERBS OF DEDUCTIONQuestion 1 / 20请完成全部题目,最后查看答案与解析GRAMMAR · B1+ Exercise 1 · Exercise 1Choose the best answer.Nobody knows exactly why he died. But we think it ___ been an accident.Amight haveBcan haveCshould have保存并进入下一题 →