Answer: Transverse
Explanation:
A transverse wave is the one in which medium particles oscillated up and down perpendicular to the direction of motion of the wave. For example: electromagnetic wave is a transverse wave.
A longitudinal wave is one in which medium particles oscillate to and fro along the direction of motion of the wave. For example: sound wave is a longitudinal wave.
Thus, a slinky moving up and down would create a transverse wave because the particles are oscillating up and down perpendicular to the direction of motion of the wave.
