For traffic that does not match any of the defined SD-WAN rules, the default implicit SD-WAN rule is applied. By default, the FortiGate uses a "source-destination IP-based" algorithm, which means all traffic from a specific source IP to a specific destination IP is sent through the same interface. This ensures that a consistent path is used for traffic between the same source and destination IP addresses. Options B, C, and D do not apply because the default algorithm does not prioritize by latency, session count, or source IP alone.
Reference:
FortiOS 7.4.1 Administration Guide: SD-WAN Load Balancing Algorithms

The routing table in the exhibit shows two default routes (0.0.0.0/0) with different administrative distances:
The default route through port2 has an administrative distance of 20.
The default route through port1 has an administrative distance of 10.
Administrative distance determines the priority of the route; a lower value is preferred. Here, the route through port1 with an administrative distance of 10 is the preferred route. The route through port2 with an administrative distance of 20 acts as a standby or backup route. If the primary route (port1) fails or is unavailable, traffic will then be routed through port2.
Regarding the statement that the port2 interface is marked as inactive, there is no indication in the routing table that port2 is inactive. Similarly, all the routes displayed are not necessarily installed in the FortiGate routing table, as the table could include both active and backup routes.
Reference:
FortiOS 7.4.1 Administration Guide: Default route configuration
FortiOS 7.4.1 Administration Guide: Routing table explanation

Based on the system performance output provided, the memory usage on the FortiGate device is at 90%, which is above the green threshold (82%) but below the red threshold (88%). Given this high memory usage, the FortiGate device will enter "conserve mode" to prevent further resource exhaustion. In conserve mode:
B . FortiGate has entered conserve mode: When the memory usage reaches or exceeds certain thresholds (in this case, the green and red thresholds), the FortiGate enters conserve mode to protect itself from running out of memory entirely. This mode limits some functionalities to reduce memory usage and avoid a potential system crash.
D . Administrators can access FortiGate only through the console port: During conserve mode, administrative access might be restricted, and administrators may only be able to connect to the device via the console port. This restriction is in place to ensure that the FortiGate can be managed directly, even under low resource conditions.
The other options are not correct:
A . FortiGate will start sending all files to FortiSandbox for inspection: This is unrelated to memory usage and conserve mode.
C . Administrators cannot change the configuration: While access may be limited, configuration changes can still be made via the console port.
Reference
FortiOS 7.4.1 Administration Guide - Monitoring System Resources and Performance, page 325.
FortiOS 7.4.1 Administration Guide - Conserve Mode, page 330.

If fortigate is used as an SSL VPN client, it needs a ssl virtual tunnel interface to connect to the SSL VPN server. This is the client virtual interface that the vpn server will assign the temporary IP address to during the lifetime of an ssl connection. The SSL VPN server also needs a correct CA certificate to authenticate/trust client's certificate.

The On Demand mode for Dead Peer Detection (DPD) on FortiGate sends DPD probes only when there is outbound traffic and no response from the peer. This mode is used to detect if the peer is still available without continuously sending DPD probes, reducing unnecessary traffic.