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: Nonketotic lactic acidosis was present in one and ketosis without a known serum lactate level was present in the other .
### Output Text:
Nonketotic lactic acidosis was present in one and ketosis without a known serum <span class="chemical">lactate</span> level was present in the other . 