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: Borderline hypertensive men ( n = 24 ) were selected with screening systolic blood pressure ( BP ) of 140 to 160 mm Hg and / or diastolic BP 90 to 99 mm Hg .
### Output Text:
Borderline hypertensive men ( n = 24 ) were selected with screening systolic blood pressure ( BP ) of 140 to 160 mm Hg and / or diastolic BP 90 to 99 mm Hg . 