What is the main difference between a longitudinal wave and a transverse wave? 
A.A longitudinal wave travels faster than a transverse wave. 
B.A transverse wave always has a larger amplitude than a longitudinal wave. 
C.The motion of the medium is parallel to a longitudinal wave and perpendicular to a transverse wave. 
D.The frequency is directly proportional to wavelength in a longitudinal wave but inversely proportional in a transverse wave.