CHOOSE THE BEST ANSWER OF EACH SENTENCE

19. - BAI LUYEN TAP THI HOC KY II KHOI 10 TRON BO DAY DU
BAI LUYEN TAP THI HOC KY II KHOI 10 TRON BO DAY DU

19. He ______ for you until you ______ him.

a. had waited / phoned b. have waited / phoned c. waited / had phoned d. waited / phoned