Final answer:
The correct sea level pressure in the ISA is 1013.2 mb, equivalent to 1 atm.
Step-by-step explanation:
In the International Standard Atmosphere (ISA), sea level pressure is taken to be 1013.2 mb (millibars), which is equivalent to 1 atm (atmosphere). This pressure is also expressed as 1.013 × 105 Pa (Pascals) or 760 mm Hg (millimeters of mercury), as per atmospheric science conventions. Option B, 1013.2 mb, is the correct choice among the provided options.