Bob was absent ; he __________ sick again.Đoạn văn26/40Bob was absent ; he __________ sick again.must bemust be beingmustn’t have beenmust have beenGiải thíchĐáp án đúng: D Giải thích: must have been: có lẽ đã Dịch: Bob lại nghỉ, chắc anh ấy lại ốm rồi.