1. The mother asked her daughter where she had been. ( Reported speech, hiện tại hoàn thành = > quá khứ hoàn thành )
2. John told his mother he didn't know how to do this exercise. ( said to = > told, hiện tại đơn = > quá khứ đơn )
3. He told her she was his friend. ( reported speech, said to = > told, hiện tại đơn = > quá khứ đơn )
4. He asked me why I studied English. ( Reported speech, hiện tại đơn = > quá khứ đơn )
5. If he polished his shoes, he would look smart. ( Câu điều kiện loại 2 : If + S + V(quá khứ đơn), S + would/could/... + V(inf) + O )