用所给单词的适当形式填空

1．There are many ________ in the box．

2．I hope you will understand the ________ of study．

3．If more and more wetlands disappear, there will be ________ and ________(little)space for plants, animals and birds．

4．________ and ________(many)birds are in danger because they do not have enough space．

5．It is ________ for you to cross the road．