Which protocol should be used for the connection between ATA1 and the Cisco Unified CallManager Express?

Exhibit:

You work as a network administrator at Domain.com. Please study the exhibit very carefully. Which protocol should be used for the connection between ATA1 and the Cisco Unified CallManager Express?

A.
FXS

B.
SCCP

C.
SIP

D.
MGCP

E.
H.323