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 most common adverse events were nausea ( 17 . 2 % and 16 . 1 % ; 95 % CI , - 3 . 7 to 6 . 0 ) , hiccups ( 10 . 7 % and 6 . 6 % ; 95 % CI , 0 . 5 to 7 . 8 ) , and headache ( 8 . 7 % and 9 . 9 % ; 95 % Cl , - 5 . 0 to 2 . 6 ) .
### Output Text:
The most common adverse events were nausea ( 17 . 2 % and 16 . 1 % ; 95 % CI , - 3 . 7 to 6 . 0 ) , hiccups ( 10 . 7 % and 6 . 6 % ; 95 % CI , 0 . 5 to 7 . 8 ) , and headache ( 8 . 7 % and 9 . 9 % ; 95 % Cl , - 5 . 0 to 2 . 6 ) . 