1. Minh hasn't written to his pen pal for five months.

2. I haven't visited Kuala Lumpur for 3 years

3. How long have you studied English?

 - Chia thì hiện tại hoàn thành, vì nó diễn tả một hành động bắt đầu từ quá khứ, vẫn còn đến hiện tại, và có thể kéo dài đến tương lai.

4. They have built this house for 2 months (giải thích như câu 3)

5. My father has worked in this factory since last week.

6. I have never visited Scotland before

1 Minh hasn't written to his pen pal for five months 

2 I haven't visited Kuala Lumpur for 3 years 

3 How long have you studied English ? 

4 They have built this house for 2 months 

5 My father has worked in this factory since last week 

6 I haven't visited Scotland before 

Nocopy 

@gladbach