21（2011·河南鹤壁高中高三第三次考试）I can’t advise you what to do and what not to do — it’s a _________ of conscience.
A. matter B. event C. thing D. problem
22（2010·河北省衡水中学三模A卷）7．Mike seldom asks ______ questions in class, but today he raised ______ fairly good one．
A．/; a B．the; a C．/; the D．/; /
