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: Clinical response was assessed on the basis of signs and symptoms and sinus radiograph or computed tomography results .
### Output Text:
Clinical response was assessed on the basis of signs and symptoms and sinus radiograph or computed tomography results . 