9. She missed the train because she was late.

• If she hadn't been late, she would have caught the train. (This changes "was" to the past perfect subjunctive "hadn't been" to show a hypothetical situation in the past.)

10. She didn't speak to him because she was so shy.

• If she hadn't been so shy, she would have spoken to him. (Same logic as sentence 9)

11. I can buy this house because Hoa lends me some money.

• If Hoa didn't lend me some money, I wouldn't be able to buy this house. (Here, we use the simple past tense "didn't lend" to show a consequence in the present)

12. Mary felt sick because she drank too much wine.

• If Mary hadn't drunk too much wine, she wouldn't feel sick. (Past perfect subjunctive for a hypothetical situation)

13. She works hard so she gets high wages.

• If she didn't work hard, she wouldn't get high wages. (Simple past for consequence)

14. If you had driven more carefully, we wouldn't have had that accident. (Correct sentence, already in second conditional)

15. If he were late, he would apologise. (Correct sentence, already in third conditional)

16. If the weather is fine, we will go on a picnic. (Present tense for the condition and future tense for the outcome)

• OR Should the weather be fine, we will go on a picnic. (Alternative using "should" for a suggestion)

17. She won't go to school if she doesn't feel better. (Correct sentence, already in zero conditional)

18. She doesn't take any exercise, so she is overweight.

• If she took some exercise, she wouldn't be overweight. (Simple present for the condition and present state)

19. He doesn't have a bicycle, so he always goes to class late.

• If he had a bicycle, he wouldn't always go to class late. (Simple past for the condition and present habitual action)

20. I am bad at English, so I can't do homework.

• If I were good at English, I could do the homework. (Subjunctive "were" for a hypothetical situation)

21. He doesn't practice speaking French, so he doesn't speak it fluently.

• If he practiced speaking French, he would speak it fluently. (Simple past for the condition and present state)

22. They are poor, so they can't help us.

• If they weren't poor, they could help us. (Subjunctive "weren't" for a hypothetical situation)

23. He didn't hurry, so he missed the train.

• If he had hurried, he wouldn't have missed the train. (Past perfect for the condition)

24. We didn't go because it rained.

• If it hadn't rained, we would have gone. (Past perfect for the condition)

25. We got lost because we didn't have a map.

• If we had had a map, we wouldn't have gotten lost. (Past perfect for the condition)