05. If you (watch) the kettle it (never boil).
06. If you (keep) right on you (get) there eventually.
07. Unless you (work) hard you (never get) anywhere.
08. If Mr. Jones (call) (tell) him I have gone to Siberia.
09. They (not do) it if they (not have) the time.
10. If he (want) to get up early he (have to go) to bed before midnight.
11. If you arrive early, you (have) to wait.
12. If you arrived early, you (have) to wait.
13. If you had arrived early, you (have) to wait.
14. They (help) you if they can. ...................................
15. They (help) you if they could.
16. They (help) you if they could have.
17. If you drink too much you (be) sick.
18. Unless you work hard you (not pass) your test.
19. If you stop smoking you (live) longer.
20. Practice hard and your English (improve).