下列哪几个组件有主备的概念（）。
A.ctilink
B.ccsapp
C.ctiserver
D.webm
E.ivr
参考答案：A, B, C, D
—I rang you at about nine, but there was no reply.
—Oh, that was probably I was seeing the doctor.
A．why
B．when
C．what
D．that
什么是变浆距控制？它有哪些特点？
