I want to have a pen friend, hopeful a girl in her early twenties, and with interests similar with mine. In my mind, she is someone who are interested in travelling, swimming, and play table tennis. Besides, it would be better for her to have pet dog as I keep one at home for some time.

Although we are thousand of miles away from each other, but I can share with her our travelling experiences, taking care of pets, or whatever we had in common. And I believe I will improve her English by doing so and learns more about her country.

空载无励磁变转速工况试验是判断振动是否由（）不平衡所引起的一种试验。

A、机组转动部件质量；

B、机组电磁力；

C、过水系统的水力；