题目

He is careless and always makes some mistakes in his homework. So he  _________ his exam again. A. improved                 B. failed     C. thought                 D. planned 答案：B现有四个函数：①；②；③；④的图象（部分）如下：   则按照从左到右图象对应的函数序号安排正确的一组是 A.①④②③         B.①④③②　  C.④①②③　  D.③④②①