根据句义完成句中已给出首字母的单词。将每个完整的单词写在各小题的横线上。

1．They are s         to study hard．

2．Liu Xiang is the pride of Chinese．We are all p         of him．

3．Flooding is one of the b         problems in the world．

4．Everyone should protect our e        ．

5．Every time I wanted to give up, my teacher would e         me to try best．