Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
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 . 

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