The issue described pertains to the establishment of a tunnel (likely a CAPWAP tunnel for management purposes between FortiGate and FortiSwitch). Based on typical error analysis in tunnel setup scenarios:
The CAPWAP tunnel failed to come up due to a mismatch in time (Option C): This answer is plausible because time synchronization is crucial for security protocols that underpin tunnel establishments, such as DTLS (Datagram Transport Layer Security) used within CAPWAP tunnels. If the clocks on FortiGate and FortiSwitch are significantly out of sync, the security handshake (which can include timestamp validation) could fail, preventing the tunnel from coming up.
Reference:
Fortinet's technical documentation typically outlines the importance of time synchronization for secure communications. In CAPWAP/DLTS scenarios, precise time matching is crucial to ensure that the cryptographic parameters align correctly during the handshake process.

Switch-controller-dhcp-snooping-verify-mac verifies the destination MAC address to protect against DHCP exhaustion attacks (B): This feature of DHCP snooping helps prevent DHCP exhaustion attacks by ensuring that the destination MAC addresses in DHCP packets match the MAC addresses learned by the switch. This check helps prevent attackers from overwhelming the DHCP server with requests from spoofed MAC addresses.
Settings related to DHCP option 82 are only configurable through the CLI (D): DHCP Option 82 is used for "agent information," and it's typically used in network environments where additional information between DHCP clients and servers is necessary for policy and billing purposes. Configuration of these settings in FortiSwitch is only available through the Command Line Interface (CLI), not the Graphical User Interface (GUI).

The two reasons why port1 can be shut down are loop guard protection and Spanning Tree Protocol (STP).
Loop guard protection: This is a feature that helps to prevent switching loops in a network.expand_more A loop guard can be configured on a port to monitor for specific traffic patterns that indicate a loop. If loop guard protection detects a loop, it will shut down the port to prevent the loop from causing problems.
STP: STP is a protocol that helps to prevent switching loops.expand_more When multiple paths exist between two network devices, STP will block all but one of the paths, creating a loop-free topology.expand_more If STP detects a loop, it will shut down the ports that are involved in the loop.
In the exhibit, both ports 1 and 2 are configured with the same native VLAN 10. This configuration could create a switching loop if both ports are connected to devices on the same network segment. If a loop occurs, loop guard protection or STP could shut down port1 to prevent the loop from causing problems.
Reference:
Fortinet FortiSwitch 7.2 Administration Guide https://docs.fortinet.com/document/fortigate/7.4.3/administration-guide/954635/getting-started

Pag 232, FortiSwitch_7.2_Study_Guide-Online "However, if you want to authenticate each device behind a port, and optionally, grant each device a different access level based on the credentials provided, then MAC-based is required."