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: OBJECTIVE : To quantify specific clinical predictors of reduction in renal function in patients with CHF who are prescribed angiotensin - converting enzyme inhibitor therapy .
### Output Text:
OBJECTIVE : To quantify specific clinical predictors of reduction in renal function in patients with CHF who are prescribed <span class="chemical">angiotensin</span> - converting enzyme inhibitor therapy . 