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: The mean lowest BIS score for any recalled word was 91 . 5 ( + / - 11 . 1 ; range 79 to 98 ) , and no words were recalled when the corresponding BIS score was less than 90 .
### Output Text:
The mean lowest BIS score for any recalled word was 91 . 5 ( + / - 11 . 1 ; range 79 to 98 ) , and no words were recalled when the corresponding BIS score was less than 90 . 