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: This study investigated behavioral phenotypes and AChE activity in male mice following BPA exposure during puberty .
### Output Text:
This study investigated behavioral phenotypes and AChE activity in male mice following <span class="chemical">BPA</span> exposure during puberty . 