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: High PELD and Child - Pugh scores before LT and high post - operative serum Tbil may be contributory risk factors for TAC - related seizures .
### Output Text:
High PELD and Child - Pugh scores before LT and high post - operative serum Tbil may be contributory risk factors for <span class="chemical">TAC</span> - related seizures . 