Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
modification : this agreement may not be modified except by a revised terms of service posted by vimeo on the vimeo site or a written amendment signed by an authorized representative of vimeo . 

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