题目内容：

用括号内所给单词的适当形式填空。

1.It usually takes me half an hour __________ (walk) to school.

2.The government should pay much attention to the __________ (increase) population.

3.The grand piano takes up too much __________ (room).。

4.I think Beijing is one of the ___________ (beautiful) places in the world.

5.No one __________ (know) when he will be back.