How should pressure be maintained to create a line of even thickness with a brush?

Correct answer: Nearly constant

Line thickness depends mainly on brush pressure and the spread of the bristles. Maintaining nearly constant pressure keeps the brush contact reasonably steady, producing a line of even width. Therefore option C is correct. Constantly changing pressure creates variation, strong initial pressure makes one end thicker, and extra pressure only at the end changes the finish rather than keeping the whole line uniform.