which protocol is used for label exchange and PW signalling?

With VPLS, which protocol is used for label exchange and PW signalling?

A.
MP-BGP

B.
LDP

C.
BGP

D.
MTP

E.
Directed LDP

F.
IGP

Explanation:
Using a directed LDP session, each provider edge advertises a virtual circuit label mapping that is

used as part of the label stack imposed on the Ethernet frames by the ingress provider edge
during packet forwarding.