三相异步电动机振动的原因有轴承故障，定转子相擦，机壳的刚度不够，电动机缺相运行等。（）
参考答案：对
小题1:Who invented the sport of badminton?
A．Indians.
B．British
C．Chinese.
D．Koreans.小题2:Which of these sports appeared earliest at the Olympics?
A．Archery.
B．Badminton.
C．Taekwondo.
D．Football.小题3:Which of the following pictures shows the sport of "Taekwondo"?
简述细胞有丝分裂和减数分裂各自的遗传学意义？
