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: METHODS : Thoracic aorta of male Sprague - Dawley rats was exposed to 0 . 5M CaCl ( 2 ) or normal saline ( NaCl ) .
### Output Text:
METHODS : Thoracic aorta of male Sprague - Dawley rats was exposed to 0 . 5M <span class="chemical">CaCl ( 2 )</span> or normal saline ( <span class="chemical">NaCl</span> ) . 