which configuration mode is a route distinguisher configured in a Cisco IOS XR router?

In which configuration mode is a route distinguisher configured in a Cisco IOS XR router?

A.
config-vrf

B.
config-vrf-af

C.
config-bgp

D.
config-bgp-af

E.
config-bgp-vrf

Explanation:
http://www.cisco.com/en/US/docs/ios_xr_sw/iosxr_r3.6/routing/configuration/guide/rc36book.pdf