用方框中所给单词的适当形式填空，每词仅用一次。

小题1:Teachers often tell their students about the _________ of learning how to learn.

小题2:Kathy is an _______ and friendly girl, her teachers all like her.

小题3:I prefer lemons to apples. I like the sour _________.

小题4:Think it over before you make a ________.

小题5:We were _________ into four groups by Mr. Zeng at the beginning of the game.

硬度与强度之间没有一定的关系。