What command is used to force an update on the FortiGuard services?

The command used to force an update on the FortiGuard services is indeed "execute update-now." This command specifically instructs the FortiGate device to immediately initiate the update process for FortiGuard services, which include antivirus signatures, intrusion prevention system (IPS) updates, and other security service updates provided by FortiGuard.

Using this command ensures that the device retrieves the latest security updates, which is crucial for maintaining optimal security posture and protecting against newly discovered threats. Regular updates from FortiGuard help ensure that the security measures in place are current and effective.

The other answer choices do not represent valid commands for updating FortiGuard services. Thus, recognizing the correct command not only demonstrates understanding of FortiGate's operational commands but also highlights the importance of keeping security services up to date.