口腔医生操作中最易感染的是
A．真菌B．病毒C．细菌D．支原体E．放线菌
参考答案：B
--- ______ do you play football?
--- Once a week.
A．How much
B．How long
C．How often
D．How far
完成下列单位换算：①5000V=______kV=______mV．②15Ω=______ kΩ
