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 _______.
A. falls.
B. rises.
C. does not change.