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: Male Wistar rats were challenged intragastrically once daily for 9 days with 1 . 0 ml / kg of corn oil containing vitamin D2 and cholesterol to induce atherosclerosis .
### Output Text:
Male Wistar rats were challenged intragastrically once daily for 9 days with 1 . 0 ml / kg of corn oil containing <span class="chemical">vitamin D2</span> and <span class="chemical">cholesterol</span> to induce atherosclerosis . 