1. joined => join

2. would make => made

3. showed => show

4. don't tell => tell

5. is => was

6. √ đúng

7. didn't make => wouldn't make

8. √ đúng

9. park => parked

10. could win => win

=>
1. Pollution can be reduced if we join hands to preven it.
2. If farmers made use of pesticide more wisely, the soil would not be poisoned.
3. I won't believe unless you show me the evidence.
4. Unles you tell me the truth, I won't help you.
5. If James were more outgoing, he would have more friends.

6. Đúng
7. If you paid more attention to what I said, you wouldn't make so many mistakes.
8. Đúng
9. You will be punished if you park your car here.
10. If you win the competition, we will have a celebration.