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: Milk - alkali syndrome induced by 1 , 25 ( OH ) 2D in a patient with hypoparathyroidism .
### Output Text:
Milk - alkali syndrome induced by <span class="chemical">1 , 25 ( OH ) 2D</span> in a patient with hypoparathyroidism . 