The correct option is C dull
The word 'glossy' refers to something shiny and smooth.
Option A, rough refers to having an uneven and irregular surface.
Option B, crude refers to being in a natural or raw state
Option C, dull refers lacking brightness, vividness or sheen.
Option D, ugly refers to being unpleasant or repulsive.
Thus, according to the meaning, the word 'dull' is the opposite of the word 'glossy'.