防止伺服电动机“自转”现象发生的方法（）
A.增大定子的电阻
B.减小转子的电阻
C.增大转子的电阻
D.减小定子的电阻
参考答案：C
It is virtually impossible to () the number of people in the world who have acquired an adequate working knowledge of English in addition to their own languages.
A. appraise
B. evaluate
C. assess
D. estimate
黄、白、蓝三个球，从左到右顺次排序，有几种排法( )
A．4
B．6
C．8
D．10
