题目内容：

用所给单词的正确形式填空，使句子意思完整。

1.It isn't easy _________(become) good English speakers.   

2.On the __________(three) floor, there is a drugstore.     

3.There are some ___________(different) in every country.   

4.When we heard the funny story, we couldn't stop __________(laugh).  

5.We should speak to our teacher __________(polite).