Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
children under thirteen ( 13 ) years of age are allowed to participate in contests . 

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