A marathon runner is training for her next race. She moves from sea level (barometric pressure 760 mm Hg) to high altitude (barometric pressure 500 mm Hg). What is the difference in the partial pressure of oxygen between sea level and the runner's new training location at altitude (500 mm Hg)?
A. 35 mm Hg
B. 44 mm Hg
C. 54 mm Hg
D. 70 mm Hg
E. 82 mm Hg