Which negotiation is initiated by setting an EtherChannel mode to auto on an interface?

Which negotiation is initiated by setting an EtherChannel mode to auto on an interface?

A.
to create anEtherChannel

B.
to create anEtherChannel only if an LACP is received

C.
to create an EtherChannel only if a PAgP packet is received

D.
to place the interface in anEtherChannel if the connected interface is also in auto mode