Question

______ move material back and forth. transverse waves longitudinal waves wavelengths none of the above

Explanation:

Longitudinal waves cause particles in a medium to move back - and - forth parallel to the direction of wave propagation. Transverse waves move particles perpendicular to the wave direction, and wavelength is a property of a wave, not a type of wave that moves material back and forth in the described way.

Answer:

B. Longitudinal waves