Here's why:
* Transverse waves involve oscillations perpendicular to the direction of energy propagation. Imagine a rope tied to a wall and you shake it up and down. The wave travels horizontally (direction of energy propagation) while the rope oscillates vertically.
* Longitudinal waves involve oscillations parallel to the direction of energy propagation. Think of a spring where you compress and expand one end. The compression and expansion travel along the spring, with the individual coils moving back and forth in the same direction as the wave travels.
Since the question emphasizes a definite direction of energy transmission, the answer is a transverse wave.
