1. Đáp án:
- 18: "My boyfriend is the most patient man I meet."
- 17: "I have lived in the house since 2006."
- "I have written three poems about her fatherland so far."
- "I have learned English for 3 years."
- "I have never eaten hot food before."
- "Maybe she won't come this afternoon. How long have you been waiting?"
- "Up to now we have not spoken."
- "She has not worked for her."
- "I have ridden my bike to school since I was 7 years old."
- "I have sent her post three times but I still don't understand what she means."
- "I have traveled to Nha Trang several times."
- "I have worked as a teacher for almost 5 years."
- "I have studied almost every lesson in this book so far."
- "I have traveled by air many times in the past."
- "I have had trouble with my car since then."
- "I had trouble with my car last week. However, I have had it fixed."
- "Over the last 10 years, they have not seen him."
- "They have become close friends."

2. Giải thích:
- Các câu trên đều sử dụng thì hiện tại hoàn thành (Present Perfect) để diễn tả hành động đã xảy ra trong quá khứ nhưng có liên quan đến hiện tại. 
- Câu 18 sử dụng "the most patient man" để chỉ ra rằng người bạn trai là người kiên nhẫn nhất mà người nói đã gặp.
- Câu 17 sử dụng "have lived" để chỉ thời gian sống trong ngôi nhà từ năm 2006 đến nay.
- Các câu khác cũng tương tự, sử dụng cấu trúc "have + V3" để diễn tả các hành động đã xảy ra và có ảnh hưởng đến hiện tại, hoặc để nói về những trải nghiệm trong quá khứ. 
- Một số câu như "have not seen" hay "have not worked" thể hiện sự chưa hoàn thành của hành động cho đến thời điểm hiện tại.

12. I don't live with my family now and we haven't seen each other for five years.

13. I haven't bought this house since 2008.

14. She has written three poems about her fatherland so far.

15. He hasn't started yet.

16. My boyfriend is the most gallant man I have met.

17. She has taught me English for 3 years.

18. I haven't tried hot food before.

19. Maybe she won't come this afternoon. How long have you waited for her?

20. He has been driving to work on my bike to school since I was 7 years old.

21. I have read her post three times but I still don't understand what she means.

22. Up to now we haven't spoken23. We have traveled to Nha Trang several times.

24. Yesterday I studied almost every lesson in this book so far since I became a teacher for almost 5 years.

25. He and his wife have traveled by air many times in the past.

26. I had a little trouble with my car last week. However, I haven't had any trouble with my car since then.

27. Over the last 10 years, they haven't seen each other.

28. They have become close friends over the last few years.