What is the reason for this issue?

A network administrator notices that remote access VPN users are not reachable from inside the network. It is determined that routing is configured correctly, however return traffic is entering the firewall but not leaving it.

What is the reason for this issue?
A . A manual NAT exemption rule does not exist at the top of the NAT table.
B . An external NAT IP address is not configured.
C . An external NAT IP address is configured to match the wrong interface.
D . An object NAT exemption rule does not exist at the top of the NAT table.

Answer: A

Explanation:

https://www.cisco.com/c/en/us/support/docs/security/firepower-management-center/212702-configure-and-verify-nat-on-ftd.html