If traffic does not match any zone-based or global security policy, the SRX applies the default security policy, which denies and discards the traffic silently. This ensures that only explicitly permitted traffic is allowed through the firewall.

When a logical interface is assigned to a security zone, it is removed from the null zone and becomes part of that zone's security policy domain.
Interfaces that are not explicitly assigned to any security zone are placed in the null zone by default, making them transit interfaces without security policy processing.

When source NAT uses a pool of addresses from the same subnet as the egress interface, the firewall must respond to ARP requests for those NAT pool IPs. Without this, upstream devices would not know how to forward traffic destined for those IPs.
Proxy ARP is required (Option D). It enables the SRX to answer ARP requests on behalf of the NAT pool addresses.
Static NAT (Option A) is unrelated and maps one-to-one, not required here.
Dynamic DNS (Option B) has no relation to NAT pools.
Destination NAT (Option C) applies to inbound translations, not outbound source NAT pools.
Correct Feature: Proxy ARP

When the source NAT address pool belongs to the same subnet as the egress interface, the SRX must respond to ARP requests for those translated IPs. Enabling proxy ARP allows the firewall to reply on behalf of those NAT pool addresses, ensuring proper packet delivery.

The policy table applies to traffic from the Trust zone to the Untrust zone. The source prefix 172.25.11.0/24 and destination prefix 10.1.0.0/16 are matched for FTP, SSH, HTTPS, and ping actions. FTP traffic from 172.25.11.11 to 10.1.0.10 matches the FTP deny policy, so option A is correct. SSH traffic from 172.25.11.10 to 10.1.0.10 matches the SSH permit policy, so option C is correct. Ping from 172.25.11.100 to 10.1.0.10 is permitted, not denied, because the ping policy permits it. Option D reverses the source and destination direction and does not match the displayed Trust-to-Untrust policy table. Security policies are matched using zone context, source address, destination address, and application.