What is the most secure way to configure the firewall rule?

An administrator is using vSphere Web Client to configure the firewall to allow specific third-party application SSH access to an ESXi Host.

What is the most secure way to configure the firewall rule?
A . Specify remote IP subnet range in IP List.
B . Use Allow connection from any IP address.
C . Disable the firewall.
D . Enable lockdown mode.

Answer: A