Answer:
D. The end of a slinky is moved vertically up and down to simulate a wave.
Step-by-step explanation:
A Slinky is a compact helical coiled toy that can perform many number of tricks such as stretching it-self and come back in its original shape.
A slinky here is used as a model by a scientist to stimulate a wave or to understand the concept of the wave. To study the nature of waves, slinky is used to create waves by moving vertically up and down that leads to the vibration or disturbance in a medium.
Hence, the correct answer is "D. The end of a slinky is moved vertically up and down to simulate a wave."