In the sentence extracted from biomedical literature, identify all the chemical entities. The required answer format is the same sentence with HTML <span> tags to mark up specific entities. 
### Entity Markup Guides:
Use <span class="chemical"> to denote a chemical.

### Input Text: The patients were randomly allocated to one of three groups ; those in group A ( n = 10 ) were subjected to controlled hypotension alone , those in group B ( n = 10 ) to haemodilution alone and those in group C ( n = 10 ) to both controlled hypotension and haemodilution .
### Output Text:
The patients were randomly allocated to one of three groups ; those in group A ( n = 10 ) were subjected to controlled hypotension alone , those in group B ( n = 10 ) to haemodilution alone and those in group C ( n = 10 ) to both controlled hypotension and haemodilution . 