Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
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nonprofits , and not airbnb , are responsible for determining what , if any , portion of their listing fee is a charitable contribution and for providing guests charitable tax receipts for any applicable charitable contributions . 

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. OPTIONS: ["Unilateral change", "Contract by using", "Arbitration", "Unilateral termination", "Choice of law", "Content removal", "Limitation of liability", "None", "Jurisdiction"].