Which statement is true when implementing a router with a dynamic public IP address in a crypto map based site-to-site VPN?

Which statement is true when implementing a router with a dynamic public IP address in a crypto map based site-to-site VPN?
A. The router must be configured with a dynamic crypto map.
B. Certificates are always used for phase 1 authentication.
C. The tunnel establishment will fail if the router is configured as a responder only.
D. The router and the peer router must have NAT traversal enabled.