which statement is correct?

You are asked to implement an IPsec VPN between your main office and a new remote
office. The remote office receives its IKE gateway address from their ISP dynamically.
Regarding this scenario, which statement is correct?

A.
Configure the dynamic-host-address option as the IKE identity.

B.
Configure the unnumbered option as the IKE identity.

C.
Configure a dynamic host configuration name (DHCN) as the IKE identity.

D.
Configure a fully qualified domain name (FQDN) as the IKE identity.