In Photoshop's Dust & Scratches Filter, the Threshold Slider

In Photoshop's Dust & Scratches filter, the Threshold slider:

A) Determines the resolution of the file.
B) Increases or decreases the size of the area search for the dissimilar pixels.
C) Increases the amount of blur in the image.
D) Determines how different the pixels should be before considering them dust or scratches.