What two devices can be connected to a router WAN serial interface that can provide clocking? (Choose two.)

A.
CSU/DSU

B.
switch

C.
modem

D.
hub

Explanation:
A router DTE interface must receive a clock rate from the DCE end and the rate can be provided by either a
CSU/DSU or a modem. Therefore, the connection between the local router and the service provider can be
successfully completed by adding either of these devices between the service provider and the local router.
Switches and hubs are neither capable of providing the clock rate nor able to complete the connection between
the local router and the service provider.
Objective:
Network Fundamentals
Sub-Objective:
Describe the impact of infrastructure components in an enterprise network

Cisco Documentation > Internetworking Technology Handbook > Introduction to WAN Technologies