题目

The cartoon “Pleasant Goat and Big Big Wolf” appeals so much to children         it caters well to their taste. A. that              B. which             C. because        D. while   答案：C13．已知函数f（x）=sin2x，为了得到g（x）=cos2x的图象，只要将y=f（x）的图象（　　）A．向左平移$\frac{π}{2}$个单位长度B．向右平移$\frac{π}{2}$个单位长度C．向左平移$\frac{π}{4}$个单位长度D．向右平移$\frac{π}{4}$个单位长度