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: An alternate class III agent , sotalol , was also effective for the prevention of VT .
### Output Text:
An alternate class III agent , <span class="chemical">sotalol</span> , was also effective for the prevention of VT . 