By the definition of wavelength, the answer is the letter D, the wavelength would decrease.
We can see in the diagram a wave motion.
A wave has some characteristics:
- Has an amplitude, the distance from 0 to the crest (highest point in the y-direction, point (3) in the figure) it would see in the figure as (2)
- Has wavelength, the distance between the crests.
- Has a trough, the lowest point in the y-direction.
Now, if we increase the distance of the crests, by the definition shown above, we will increase the wavelength.
Therefore, the answer is letter D, the wavelength would increase.
You can learn more about wave motion here:
