A.1/2 B.1/3 C.1/4 D.1/9
A.真空度不容易在運(yùn)行中進(jìn)行監(jiān)視 B.容易引起操作過電壓 C.所需操作功率大 D.機(jī)械壽命短
A.5% B.10% C.15% D.20%