By the time John arrived, all his friends _____________. A. have left B. would leave C. had left D. were leavingĐoạn văn5/40Mark the letter A, B, C, or D to indicate the most suitable answer to each of the following questions. By the time John arrived, all his friends _____________.have leftwould leavehad leftwere leavingGiải thíchChọn đáp án C