阅读下面材料，在空白处填入适当的内容（1个单词）或括号内单词的正确形式。
In this constantly changing world, how to put the knowledge      (gain) every day into      (real) has interested numerous people. As a proverb goes, “Knowledge is a treasure, but practice is the key       it.” Apparently, this saying     (try) to deliver the message       we ought not to stop practicing it if we      (true) want to master the knowledge we learn,
There are several reasons       (account) for this statement. To begin with, human beings are forgetful beings; therefore, only when we use knowledge, make     (mistake), and try to use it again will we be able to remember it by our heart. Moreover, knowledge has become growingly complicated and we can seldom grasp the essence of it if we do not practice it again and again.
Practicing, to sum up,      (be) of greatest importance for those who are determined to learn knowledge well. As a student, I hope that the young can focus more attention on practicing       they learn.