Identify the unfair aspect with respect to the sentence extracted from an online Terms of Service:
```
when you use the fitbit service after a modification becomes effective , you are telling us that you accept the modified terms . 

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