正常运行时，正电刷的磨损程度较负电刷（）。
A.厉害
B.轻微
C.相同
D.轻重不一定
参考答案：A
（安徽安庆2009教学质量监测） It is estimated by some experts that by the end of next year we a fall in house prices by 25%.
A．will see
B．see
C．has seen
D．will have seen
在实数范围内分解因式a2－12＝ ．
