III. Chọn một đáp án đúng trong số A, B, C hoặc D để hoàn thành mỗi câu sau. 16. When you last night, I A rang/have worked B. rang/ worked C. were ringing D. rang/ was working 17. Nam went to party yesterday, ? C. do they A. didn't he B. did they 18. Among all, I think English grammar is A. difficult B. more difficult in the garden, so I didn't hear the phone D. didn't he C. most difficult D. the most difficult
