How should a request be refused in assertive communication?

Correct answer: Clearly and respectfully, with an appropriate reason

Assertive refusal states the decision clearly and calmly, gives a brief honest reason when appropriate, and respects the other person. It does not require shouting, insults, or disappearing without an answer. A useful pattern is to acknowledge the request, say that it cannot be accepted, and offer an alternative if one is genuinely possible.