HÃY CHỌN MỘT ĐÁP ÁN ĐÚNG NHẤT (A, B, C HOẶC D) CHO MỖI CÂU SAU

13. - ON THI TRAC NGHIEM TIENG ANH 12BAM SAT
ON THI TRAC NGHIEM TIENG ANH 12BAM SAT

13. How many times________ them so far?

A. have you seen B. did you see C. were you seeing D. had you seen