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: RESULT ( S ) : A 36 - year - old Chinese woman developed central retinal vein occlusion after eight courses of CC .
### Output Text:
RESULT ( S ) : A 36 - year - old Chinese woman developed central retinal vein occlusion after eight courses of <span class="chemical">CC</span> . 