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 increments in BUN , creatinine , and K were reduced by 63 , 80 , and 42 % , respectively , in Group B patients compared to Group A . Response to treatment did not differ significantly between the 2 groups .
### Output Text:
The mean increments in <span class="chemical">BUN</span> , <span class="chemical">creatinine</span> , and <span class="chemical">K</span> were reduced by 63 , 80 , and 42 % , respectively , in Group B patients compared to Group A . Response to treatment did not differ significantly between the 2 groups . 