The correct answer is C because available when controls whether an action is visible to the reasoning engine for that reasoning cycle. If the action was hidden when the turn began, setting isVerified to true during that same turn does not retroactively expose the hidden action for immediate invocation. The action becomes available only when the next reasoning cycle starts and the guard condition evaluates against the updated variable state. Option A is dangerous because model intent never overrides an availability guard. Option B is wrong because treating action visibility as continuously re-evaluated inside the same turn would break deterministic gating. Salesforce documentation describes available when as a way to control flow based on state, and variables can be used in filters and action control.