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: However , a 14 % ( from 70 + / - 8 % to 60 + / - 7 % ) reduction in S ( c ) O ( 2 ) ( P < 0 . 05 ) followed with no change in CO ( 3 . 7 + / - 1 . 1 to 3 . 4 + / - 0 . 9 l min ( - 1 ) ) .
### Output Text:
However , a 14 % ( from 70 + / - 8 % to 60 + / - 7 % ) reduction in S ( c ) O ( 2 ) ( P < 0 . 05 ) followed with no change in CO ( 3 . 7 + / - 1 . 1 to 3 . 4 + / - 0 . 9 l min ( - 1 ) ) . 