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