Westerly Winds in the Upper Atmosphere at Mid-Latitudes in the Northern

Multiple Choice

Westerly winds in the upper atmosphere at mid-latitudes in the Northern Hemisphere:

A) are a result of a pressure gradient that moves air from the poles toward the equator.
B) are stronger in summer than in winter.
C) are the reason most mid-latitude storms move from west to east.
D) are moving perpendicular to 500 mb contours.