1 If I see him, I (give) him a lift.
2 The table will break if you (sit) on it.
3 If he (eat) all that, he will be ill.
4 If I find your passport, I (telephone) you.
5 The police (arrest) him, if they catch him.
6 If he (read) in bad light, he will ruin his eyes.
7 Someone (steal) your car if you leave it unlocked.
8 What will happen if my parachute (not open)?
9 If he (wash) my car, I'll give him $10.
10 If she (need) a radio, she can borrow mine.
11 If you (not go) away, I'll call the police.
12 I'll be very angry if he (make) any more mistakes.
13 If he (be) late, we'll go without him.
14 She will be absolutely furious if she (hear) about this.
15 If you put on the kettle, I (make) some tea.
16 If you give my dog a bone, he (bury) it.
17 If we leave the car here, it (not be) in anybody's way.
18 He'll be late for the train if he (not start) at once.
19 If you come late, they (not let) you in.
20 If he (go) on telling lies, nobody will believe a word he says.
21 Unless he (sell) more, he won't get much commission.
22 If I lend you $10, when you (repay) me?
23 We'll have to move upstairs if the river (rise) any higher.
24 If he (work) hard today, can he have a holiday tomorrow?
25 Ice (turn) to water if you heat it.
26 If the house (burn) down, we can claim compensation.
27 If you (not like) this one, I'll bring you another.
28 Unless you are more careful, you (have) an accident.
29 Tell him to ring me up if you (see) him.
30 If I tell you a secret, you (promise) not to tell it to anyone else?
31 If you (not believe) what I say, ask your mother.
32 If he (like) the house, will he buy it?
33 If you kindly sit down, I (make) enquiries for you.
34 Unless I have a quiet room, I (not be able) to do any work.
35 She won't open the door unless she (know) who it is.
36 Should you require anything else, please (ring) the bell for the attendant.
Source: These activities have been taken from "A Practical English Grammar. Exercises 1" by Thomson and Martinet. (Third Edition)