Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
you may also be required to register an account on the service ( an `` account '' ) . 

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