Which command must be globally enabled on a Cisco router to support IPv6?

A.
ip routing ipv6

B.
ipv6 unicast-routing

C.
ipv6 routing

D.
ip classless

E.
ipv6 cef

Explanation:
http://computernetworkingnotes.com/ipv6-features-concepts-andconfigurations/routing-with-ipv6.html (See the first para)