1.I (buy) ..... a car if you lend me some money 2.If the book (not be) ..... expensive , I'll buy it 3.I'll go out if it (not rain) ..... 4.If that hat costs much , I (buy) ..... a small one 5.If she (make) ..... that mistake again , her teacher will get angry with me 6.I will lend them some money if they (ask) ..... me 7.My dog will bark if it (hear) ..... any strange sound 8.They (let) ..... you in if you come late 9.He's waiting for his mother to come back from Chicago . If his mother (come) ..... home , he will have a lot of presents 10.The kitchen will look better if we (have) ..... red curtains 11.If we (keep on) ..... using more and more motor vehicles , we (run out) ..... of oil 12.If we (run out) ..... of oil , we (need) ..... other kind of energy 13.If we (use) ..... more oil and coal , pollution (increase) ..... 14.If pollution (increase) ..... more and more trees (die) ..... 15.If more and more trees (die) ..... the climate (change) ..... 16.If the climate (change) ..... we (meet) ..... with natural disasters 17.If we (try) ..... to control pollution , it (be) ..... very expensive 18.If you ..... (not see) me tomorrow , I ..... (call) you up 19.We're going to leave tomorrow if the weather (be) ..... nice 20.If he (speak) ..... more slowly , we will understand him