Now the air in our city is ________ than it used to be．Something must be done to stop it．

If you don’t work _______ enough, I don’t think your dream will come_______.

There is a ______ tree in our school.

 –Waiter, $ 20 for dinner, right? --I’m afraid $25, sir, for drinks are ________.

Some students are so ______ that they often make mistakes in their homework.