根据句意，用括号中所给词的适当形式填空。

( )1. Let ______  try, and I will understand.  (I)                                                                      

( )2. I have met many kind teachers in the past three years. I think I am a ______ girl. (luck)  

( )3. Life to everyone is only ______, we shouldn't waste time. (one)                      

( )4. Give up  ______! It's bad for your health. (smoke)                                      

( )5. Li Na is one of the best tennis  ______ in the world. (play)