Answer:The earthquake wave must be B: longitudinal.
Explanation:In a transverse wave, particles vibrate perpendicular to the direction of wave propagation, forming crests and troughs.
In a longitudinal wave, particles vibrate parallel to the direction of wave propagation, forming compressions and rarefactions.
Since the particles of the rock are vibrating in a north-south direction, which is parallel to the direction of wave propagation from west to east, the wave must be a longitudinal wave.