题目

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。 We may be very (please ) with the rapid progress we have made in every field of study , but we have almost done nothing ( improve ) our present examination systems which focustesting the students' memory instead of their ability . As soon as a child begins school , he enters a world of examinationwill decide his future of job . In fact , a good examination system should encourage students to think for ( they ) . But the examination system now forces the students to remember is taught 函数f（x）=Asin（ωx+ϕ）的图象如下图所示，为了得到g（x）=-Acosωx的图象，可以将f（x）的图象   （ ）A．向右平移个单位长度B．向右平移个单位长度C．向左平移个单位长度D．向左平移个单位长度