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

21. As she ________ a letter last night, the lights suddenly ________ out.

A. was writing/ went B. wrote/ went

C. was writing/ was going D. writes/ went