— _____do they surf on the internet ?

—Twice a week.

A．How soon

B．How much

C．How many

D．How often

隔离开关应动作可靠、转动灵活，合闸时触头接触良好，引线和连接线的截面与开关的额定电流及所连接的接触网当量截面相适应，引线不得有接头。