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 EF was 40 % , in the group with MP and 44 % in the group with severe MR and it can be a factor associated with clinical events in the last group .
### Output Text:
The EF was 40 % , in the group with MP and 44 % in the group with severe MR and it can be a factor associated with clinical events in the last group . 