[单选题]

The major goal of USB was to define an external expansion bus which makes adding(70)to a PC as easy as hooking up a telephone to a wall-jack. USB 2.0 is an evolution of the USB 1.1(71), providing a higher performance interface.
A．peripherals
B．outside
C．inside
D．beside

The major goal of USB was to define an external expansion bus which makes adding(70)to a PC as easy as hooking up a telephone to a wall-jack. USB 2.0 is an evolution of the USB 1.1(71), providing a higher performance interface.A．peripheralsB．outsideC．insideD．beside