1. I couldn't write to Alice because I didn't know her address.

⇒ If I know her adress ,I could write to Alice.

2. The heavy rain kept everybody from going outdoors.

⇒ If it hadn't rained heavily, everybody would have gone out

3. I didn't watch TV last night because I was busy.

⇒ If I hadn't been busy last night, I would watched TV

4. People don't see the UFO, so they don't call the National UFO Reporting Center.

⇒ If people saw the UFO, they would called the National UFO Reporting Center.

5. Thu can't swim, so she doesn't go swimming in Lam Son Swimming pool.

⇒ If Thu could swim, she would went swimming in Lam Son Swimming pool.

6. His flight was delayed so he couldn't be there on time.

⇒ If his flight wasn't delayed, he could been there on time.

7. They do not understand you because you speak too fast.

⇒ If you didn't speak too fast, they could understood you.

8. He doesn't apply for the job because he doesn't have enough qualifications.

⇒ If He had enough qualifications, he could apply for the job.

9. He never polishes his shoes, so he never looks smart.

⇒ If he polished his shoses, he could looked smart.

10. Go right now or you will be late for the train.

⇒ If you didn't go right now, you would late for the train.

1.If I know her adress ,I could write to Alice.

2.If it hadn't rained heavily, everybody would have gone out

3. If I wasn't busy last night, I would watched TV.

4. If people saw the UFO, they would called the National UFO Reporting Center.

5. If Thu could swim, she would went swimming in Lam Son Swimming pool.

6. If his flight wasn't delayed, he could been there on time.

7. If you didn't speak too fast, they could understood you.

8. If He had enough qualifications, he could apply for the job.

9. If he polished his shoses, he could looked smart.

10. If you didn't go right now, you would late for the train