9. I wish I had gone to the party last Sunday.

(wish ở quá khứ: S + wish(es) + S + QKHT)

10. The lady whom my mother has worked with for a long time is an engineer.

(whom - đại từ quan hệ thay thế cho từ her đóng vai trò làm tân ngữ)

11. As he worked hard, he passed the exam.

(As = because: bởi vì + Clause)

12. She asked me where I had gone with my friends the day before/the previous day.

( asked someone Wh_question + (câu trực tiếp thì QKĐ lùi thì ⇒ câu gián tiếp thành QKHT), "your" chuyển thành "my", "yesterday chuyển thành "the day before" or "the previous day")

13. Energy saving-bulbs should be used to save electricity.

(Active: S + should + V_bare

 Passive: S + should + be + V_pp)

14. If we had her address, we could visit her.

(Câu trên thì HTĐ ⇒ If 2: If + S + V_ed + O, S + would/could/should + V_bare)

15. He was tired. However, he stayed up late to watch the football match on TV. (bỏ but)

(này bạn tự dịch nha :)) 

16. Hong told Nga (that) she had damaged her bicycle.

(told someone (that) S + V(lùi thì) từ QKĐ ⇒ QKHT)

17. Where did we stay?

("In a lovely house" chỉ nơi chốn dùng "where")

18. Because of his illness (or being ill), he didn't go to the party.

(Because bởi vì ⇔ because of + N/V_ing)

19. If we had enough money, we could take a trip to Singapore.

(Câu trên thì HTĐ ⇒ If 2: If + S + V_ed + O, S + would/could/should + V_bare)

20. Despite having health problems, he is always smiling.

(Despite + N/ V_ing: Mặc dù)