The correct answer is C because this requirement must be enforced deterministically at the action- availability layer, not trusted to natural language instructions. In Agentforce, filters can control access to subagents and actions so the agent can use them only when defined conditions are met. For refund processing, the "Issue Refund" action should be hidden from the reasoning engine unless the account tier condition evaluates to Platinum. Option A is weak because system instructions are interpreted by the model and can be ignored or misapplied. Option B is wrong because blocking a keyword is brittle and does not validate entitlement. Action filters are the correct control because they prevent the action from being available until the business rule is satisfied.