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: The time course of events suggested that amphotericin B was the cause of the seizures in this AIDS patient .
### Output Text:
The time course of events suggested that <span class="chemical">amphotericin B</span> was the cause of the seizures in this AIDS patient . 