The house was empty when I arrived. They _ must have gone to bed3/50Mark the letter A, B, C, or D on your answer sheet to indicate the correct answer to each of the following questions. The house was empty when I arrived. They ___________. must have gone to bed should have gone to bed would have gone to bed. need have gone to bedGiải thíchĐáp án A. Dùng must have + PP để dự đoán điều gì chắc chắn đã xảy ra trong quá khứ.