Here are the sentences rewritten using "If":

1. **If the weather had been fine yesterday, we would have had a picnic in the meadow.**

2. **If he had prepared his lesson carefully, he would have gotten good marks.**

3. **If my uncle had not been poor, he could have bought that house.**

4. **If those athletes had trained hard, they could have broken past records.**

5. **If his friends had not been late, they could have caught the train.**

6. **If I were his brother, I could give him some advice.**

7. **If Daisy were here now, she could help us.**

8. **If the bicycle were new, he would want to buy it.**

9. **If the banks were not covered with weeds, we could go swimming there.**

10. **If he had learned his lesson carefully, he could have done that exercise.**

1. **If the weather had been fine yesterday, we would have had a picnic in the meadow.**

2. **If he had prepared his lesson carefully, he would have gotten good marks.**

3. **If my uncle had not been poor, he could have bought that house.**

4. **If those athletes had trained hard, they could have broken past records.**

5. **If his friends had not been late, they could have caught the train.**

6. **If I were his brother, I could give him some advice.**

7. **If Daisy were here now, she could help us.**

8. **If the bicycle were new, he would want to buy it.**

9. **If the banks were not covered with weeds, we could go swimming there.**

10. **If he had learned his lesson carefully, he could have done that exercise.**