What needs to be enabled for Unicast RPF?

A.
BGP
B.
OSPF
C.
CEF
D.
RIP
Explanation:
Cisco Express Forwarding switching must be enabled for Unicast RPF to function. This command
has been enabled by default as of IOS version 12.2. If it is not enabled, administrators can enable
it with the following global configuration command: ip cef