7．If you want to learn English well，I think it is very h_________ for you to read it every day．

6．Many economists are busy with their r_________ work to solve the economic problems of the world．

5．All the boys were _________(精疲力竭的)after they climbed up to the top of the mountain．

B．根据句意及首字母提示完成句子：

4．By end of this _________(世纪)，We'll have robots in our house to help us do housework．

3．During the long vacation，we are planning to take part in some _________(社会)activities．

2．We should have the habit of _________(回收利用)the waste things such as wastepaper，bottles，plastic bags and so on．

A．根据句意及汉语提示完成句子：

1．His father is a _________(知识渊博的)man．He knows a lot we don't know．