根据句意选词并用其适当形式填空。

Of all the ________， I think Mickey Mouse is the prettiest.
We should take action to kept water from ________.
It is a new kind of computer. Please use it ________.
---You can improve your __________ of grammar by playing this game.
---That’s very nice of you.
The little boy often looks sad because he misses his _______ lovely pet very much.