The correct option is enables safe validation and debugging in an isolated context.

Manual triggers in GitHub Actions allow the team to start a workflow only when they choose to run it. This keeps the workflow isolated from automatic events during the release freeze so pipeline changes can be tested without impacting routine runs or deployments. The team can supply inputs, inspect logs and artifacts, and iterate safely while production automation remains paused.

ensures runs are restricted to a single branch only is incorrect because manual triggers do not inherently limit execution to a single branch. Branch scoping is controlled by event filters or conditional logic, not by the manual nature of the trigger itself.

reduces job duration by parallelizing every job automatically is incorrect because manual triggers do not change how jobs are parallelized. Parallelism and execution strategy are defined in the workflow configuration through matrices or separate jobs and are never enabled automatically by choosing a manual trigger.

Cloud Scheduler is incorrect because it is a Google Cloud service for scheduled tasks and it does not provide manual GitHub Actions triggers. It is not the right tool for validating GitHub workflows during a freeze without affecting automatic runs.

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