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: This experience raises the question of the role of BMT itself as a therapeutic option for patients with uncontrolled destructive synovitis .
### Output Text:
This experience raises the question of the role of BMT itself as a therapeutic option for patients with uncontrolled destructive synovitis . 