As the value of the Hue parameter increases, the indicator The indicator shown is similar to a $\_\_\_\_\_\_\_\_\_\_\_\_\_\_\_.$

The image is a screenshot of Excel's HSL color adjusting. The indicator referred to is on the Colors window. From left to right, the colors vary by hue. Vertically, they vary by saturation.

a$.$

moves horizontally from right to left

b$.$

moves vertically from top to bottom

c$.$

does not move

d$.$

moves horizontally from left to right