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: Tumors , all papillomas , were induced in 3 rats ( 17 % ) with 0 . 25 % RA and in one rat ( 10 % ) with 0 . 05 % RA co - administration .
### Output Text:
Tumors , all papillomas , were induced in 3 rats ( 17 % ) with 0 . 25 % <span class="chemical">RA</span> and in one rat ( 10 % ) with 0 . 05 % <span class="chemical">RA</span> co - administration . 