Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
any promotion code or offer provided by us may not be used in conjunction with any other promotion code or offer , past or present . 

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