Refer to the exhibit.Which two devices can be used to complete the connection between the WAN router atthe customer site and the service provider?()<br /> <img src="https://nimg.ppkao.com/2018-07/yiyu/2018072314184977576.jpg?sign=cf7d3c8e2ae228f0d4c62c3c466f75d7&t=62d28523" />
A、modem
B、Frame Relay switch
C、CSU/DSU
D、WAN switch
E、ISDN TA