Tìm và sửa lỗi sai:
31. When I walk past the park, I saw some children play football.
32. After John eaten dinner, he wrote several letters and went to bed.
33. What did you do at 9 clock last night? I phoned you but nobody answered.
34. When I arrived at the station, the train has already left.
35. Ann and Susan have known each other during they were at school.
36. She has disappeared three days ago, and they are still looking for her now.
37. After Mrs. Wang had returned to her house from work, she was cooking dinner
38. It’s the first time I saw this film
39. After he graduates from university, he joined the army.
40. Up to now, there had been no woman being chosen the US president.