Select the correct answer. In a transverse wave, the particles of the medium move:

In a transverse wave, the particles of the medium move perpendicular to the direction of the wave's travel. This means that if the wave is moving horizontally, the individual particles of the medium, such as those in a string or water surface, oscillate up and down. A common example of this is a wave on a string; when you move the end of the string up and down, the wave travels along the length of the string while the particles of the string move in a circular or up-and-down motion.

Thus, the correct answer is that the particles of the medium move perpendicularly to the direction of the wave's propagation.