从交流通路来看，三点式LC振荡器中电感或电容的中心抽头应该与（）相连。
A、发射极
B、基极
C、集电极
D、接地端
参考答案：A
______ is permanently stored in the computer and provides a link between the hardware and other programs that run on the PC.
A．Interface
B．Operating system
C．Internet
D．Applicaion software
