牵引电动机电枢故障时，只要不是第2、5电机，切除后仍可使用电阻制动。
参考答案：错
哪项符合临产的诊断（）
A.胎头已达坐骨棘水平
B. * * 排液
C. * * 有少量血性黏液
D.规律宫缩，宫颈扩张，胎头下降
E.尿频腹胀
A box contains 100 balls, numbered from 1 to 100. If three balls are selected at random and with replacement from the box, what is the probability that the sum of the three numbers on the balls selected from the box will be odd
