三相异步电动机正常运转时，其转子转速( )旋转磁场转速。
A．大于
B．等于
C．小于
D．正比于
参考答案：C
— Why does the lake smell terrible?
— Because large quantities of water ____ . [ ]
A. have polluted
B. is being polluted
C. has been polluted
D. have been polluted
对肝硬化诊断最有价值的是（）
A.脾大
B.B超肝内回声粗糙不匀
C.肝掌，蜘蛛痣
D.肝功能试验异常
E.钡透食管下端有蚯蚓状充盈缺损
