Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
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in addition , airbnb may ( i ) keep the calendar for the listing unavailable or blocked for the dates of the cancelled booking , and/or ( ii ) impose a cancellation fee , unless the host has a valid reason for cancelling the booking pursuant to airbnb 's extenuating circumstances policy or has legitimate concerns about the guest 's behavior . 

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