第二节 语法与词汇知识（共15小题；每小题1分，满分15分）
6．It is well-known to us all that knowledge is ______ treasure, but practice is ______ key to it．
A．a; / B．a; the C．the; the D．/; the
7．Many a quarrel ______ throughout a misunderstanding．So you should talk more with him．
A．comes about B．comes across C．comes out D．comes from
