which two of these approaches can enable IPv6 tunneling between Site A and Site B over the backbone?

Refer to the exhibit

If the service provider is an IPv4-only network, which two of these approaches can enable IPv6
tunneling between Site A and Site B over the backbone? (Choose two.)

A.
DNS

B.
NeTBIOS

C.
FTP

D.
GRE tunnel

E.
L2TP v3