--- ___________ is it from Suzhou to Beijing?

--- It used to be a long way, but nowadays, it takes only five hours to get there by high-speed rail.

A．How soon

B．How much

C．How far

D．How long

KP-2A型控制箱中的主整流器采用（）整流电路。

A.三相桥式

B.单相桥式

C.二倍压

D.三相可控