Answer:

23. If Elizabeth hadn't started smoking cigaretes, she wouldn't have got a bad cold.

24. If Joan doesn't find a good job before Sep, she will stay on at school.

1/  If you don't get a visa, you can't visit the United States

2/ If we had enough money we would have gone on holiday.

3/ I wish you hadn't failed your driving test

4/ I wish I hadn't missed your birthday party.

5/ We can get into the house if someone has a key.

6/ He wishes he had invited Molly to his party

7/ If he doesn't phone his wife immediately, he won't get any information

8/ If Mr. Mills hadn't been late everyday, he wouldn't havelost his job