市电正常时，（）UPS逆变部件带负载工作。
A.后备式
B.在线式
C.以上都是
参考答案：B
—_______ at this season of year in the north?
—It's much hotter than last year. The high temperature has lasted for days. [ ]
A. How are things going
B. How are you getting on
C. What's the weather like
D. What do you do
空气制动阀电空位操作时运转位的作用是什么？
