刹车无力的原因有（）
A.分泵磨损
B.刹车片磨损
C.总泵泄压
D.刹车盘磨损
参考答案：A, B, C, D
奇函数f（x）满足对任意x∈R都有f（2+x）+f（2-x）=0，且f（1）=9，则f（2010）+f（2011）+f（2012）的值为（ ）。
The teacher asked the students _______. [ ]
A. how many trees they have planted
B. where was Yao Ming born
C. how they will deal with the problem
D. what happened to the monitor
