Which command should you use to configure a dial-peer to support T.38 fax relay and to use Cisco fax

Which command should you use to configure a dial-peer to support T.38 fax relay and to use
Cisco fax relay if T.38 fails?

A.
fax protocol t38 fallback cisco

B.
fax t38 fallback cisco

C.
fax relay t38 cisco

D.
fax relay t38 backup cisco relay