用方框中所给单词或词组的适当形式填空，每词限用一次。

many    interested   if   twentieth     talk

There are______ cars on the road in the summer than in the winter.
We’ll go to the Great Wall ______ it doesn’t rain tomorrow.
Bruce was_______ on the mobile phone when the policeman stopped her yesterday.
This book is interesting and I am________ in it.
It shows the lives of people in the_________ century.