Refer to the exhibit.

Which SIP message header is used to tunnel QSIG messages across the SIP network when the
OGW receives a call bound for the TGW?

A.
Content-TypE.application/sdp

B.
Content-TypE.application/qsig

C.
Content-TypE.message/ISUP

D.
Content-TypE.message/external-body

E.
Content-TypE.application/x-q931