题目

It is reported that the police will soon ____ the case of two missing children.A. look upon         B. look after       C. look into       D. look out      答案：   C   解析：本题考查动词短语。根据题意可知应选look  into “调查”。下列合并同类项的结果正确的是  （     ）A.a＋3a=3a    B.3a－a=2      C.3a＋b=3ab      D. a－3a=－2a