1. The last time we saw her was on Christmas.
- We haven't seen her since Christmas.

2. I haven't eaten this kind of food before.
- This is the first time I have eaten this kind of food.

3. It started raining an hour ago.
- It has been raining for an hour.

4. We haven't visited my grandfather for two months.
- The last time we visited my grandfather was two months ago.

5. I have studied English for three years.
- I began studying English three years ago.

6. My brother hasn't seen his best friend for nearly five years.
- It's been nearly five years since my brother saw his best friend.

7. When did you start learning English?
- How long have you been learning English?

8. We started living here fifteen years ago.
- We have been living here for fifteen years.

9. The last time she visited me was five years ago.
- She hasn't visited me in five years.

10. I last wrote to my uncle in July.
- I haven't written to my uncle since July.

11. It's a long time since we became close friends.
- We have been close friends for a long time.

12. Minh began to collect stamps in 2000.
- Minh has been collecting stamps since 2000.