高速旋杯式自动静电喷涂机涂料液滴雾化直径可达到（）um。
A.20～30
B.30～50
C.50～100
D.100～200
参考答案：C
He speaks English as fluently as if he__________an Englishman.
A．were
B．had been
C．is
D．has been
网络操作系统能否安装在PC机上？
