To successfully vent air from a BC: A. You need to be in a perfectly vertical position.
B. The exhaust valve you will be using must be the highest point on the air cell.
C. You must activate the BC's overpressure relief valve.
D. None of the above.

As seen in a us weather map, the h (or high) and l (or low) symbols indicate regions where surface air pressures are high or low, respectively, compared to surrounding areas. an h is plotted where the air pressure is highest and an l is plotted where the air pressure is lowest. proceeding outward and away from the center of a high pressure system, the air pressure "