1.I've done my best!
2.Helen is the most beautiful girl that I have ever seen.
3.Mr.Chang is the kindest teacher that I have ever had.
4.Nothing is more important than to  receive education.
5.We can't emphasize the importance of protecing our eyes too much.
6.There is no denying that the qualities of our living have gone from bad to worse.
7.The harder you work,the more progress you make.
8.By taking exercise,we can always stay healthy.
9.Listening to music enable us to feel relaxed.
10.On no accout can we ignore  the value of knowledge.