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: Adults chronically treated with angiotensin converting enzyme inhibitors may have a limited ability to respond to hypotension when the sympathetic response is simultaneously blocked .
### Output Text:
Adults chronically treated with <span class="chemical">angiotensin</span> converting enzyme inhibitors may have a limited ability to respond to hypotension when the sympathetic response is simultaneously blocked . 