— Could you please tell me     ?

—Tomorrow morning.

A．how I can get to the post office

B．how long can I keep the book

C．when to leave for Beijing

D．where I should take the early bus

40千瓦以上起动频繁的控制设备，按规程规定，应使用（）。

A、真空接触器

B、空气接触器

C、SF6断路器

D、一般负荷开关