Which three factors best justify WAN link redundancy between geographically dispersed sites? (Choose three.)

A.
high expense of transmitting data

B.
important traffic flows

C.
excessive packet transmission rate

D.
uncertain reliability

E.
high link utilization

F.
lack of speed

Explanation:
Explanation

WAN Backup Design
Redundancy is critical in WAN design for the remote site because of the unreliable nature of WAN links, when compared to LANs that they connect. Most enterprise edge solutions require high availability between the primary and remote site. Because WAN links have lower reliability and lack bandwidth, they are good candidates for most WAN backup designs.

Branch offices should have some type of backup strategy in the event of a primary link failure. Backup links can be either dialup, permanent WAN, or Internet-based connections.
WAN backup options are as follows:

Cisco Press CCDA 640-864 Official Certification Guide Fourth Edition, Chapter 7