Which option describes how IPsec is used for L2TP configuration on GGSN?

Which option describes how IPsec is used for L2TP configuration on GGSN?

A.
IPsec encapsulated data is sent over the L2TP tunnel.

B.
L2TP encapsulated data is sent over the IPsec tunnel.

C.
L2TP references IPsec for forwarding decisions.

D.
IPsec encapsulated data is sent between MS and GGSN, and data between LAC (GGSN)
and LNS is sent via L2TP tunnel.