Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
22.5 airbnb 's failure to enforce any right or provision in these terms will not constitute a waiver of such right or provision unless acknowledged and agreed to by us in writing . 

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