Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
we may offer free trials or other limited versions of services so that you can preview services before you purchase the full version . 

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