用方框中所给单词的适当形式填空，每词仅用一次。

Teachers often tell their students about the _________ of learning how to learn.
Kathy is an _______ and friendly girl, her teachers all like her.
I prefer lemons to apples. I like the sour _________.
Think it over before you make a ________.
We were _________ into four groups by Mr. Zeng at the beginning of the game.