分块瓦导轴承在轴瓦修刮时，检查接触面积能否达到85%，接触点能否达到（）个/cm2
A.2～4
B.1～2
C.3～6
D.1～5
参考答案：A
There _____ great changes in our country in the past twenty years. [ ]
A. have been
B. has been
C. have had
D. has had
简述动车组在过分相区时，空调装置和照明是否停电，并说明原因？
