What is a prerequisite for configuring BFD? 

Answer options:

A. Jumbo frame support must be configured on the router that is using BFD.B. All routers in the path between two BFD endpoints must have BFD enabled.
C. Cisco Express Forwarding must be enabled on all participating BFD endpoints.
D. To use BFD with BGP, the timers 3 9 command must first be configured in the BGP routing process.

C

Reference: https://www.cisco.com/c/en/us/td/docs/ios/12_0s/feature/guide/fs_bfd.html#wp1043332