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: Adverse reactions to bendrofluazide and propranolol for the treatment of mild hypertension .
### Output Text:
Adverse reactions to <span class="chemical">bendrofluazide</span> and <span class="chemical">propranolol</span> for the treatment of mild hypertension . 