On Cisco IOS XR software, how is LDP enabled on an interface?

A.
LDP is automatically enabled globally on all interfaces, when ip cef is enabled globally.

B.
LDP is enabled on each interface, using the mpls ip interface configuration command.

C.
LDP is enabled on each interface, using the interface command under mpls ldp (MPLS LDP
configuration mode).

D.
LDP is enabled globally on all interfaces, using the mpls ldp global configuration command.

E.
LDP is enabled globally on all interfaces, using the mpls ip global configuration command.

Explanation:
http://www.cisco.com/en/US/docs/ios-xml/ios/mp_ldp/configuration/12-4m/mp-ldp-12-4m-book.pdf