12. If the sun ………(to shine), we……..(to walk) into town.
13. If he……..(to have) a temperature, he……..(to see) the doctor.
14. If my friends……..(to come), I……..(to be) very happy.
15. If she……..(to earn) a lot of money, she……..(to fly) to New York.
16. If we……..(to travel) to London, we……..(to visit) the museums.
17. If you……..(to wear) sandals in the mountains, you……..(to slip) on the rocks.
18. If Rita……..(to forget) her homework, the teacher……..(to give) her a low mark.
19. If they……..(to go) to the disco, they……..(to listen) to loud music.
20. If you……..(to wait) a minute, I……..(to ask) my parents.
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