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: . Hypertension and treatment with bevacizumab appear to be additional risk factors .
### Output Text:
. Hypertension and treatment with <span class="chemical">bevacizumab</span> appear to be additional risk factors . 