Which habit is useful for achieving an even tone while shading?

Correct answer: Maintain consistent pressure and direction

The governing concept is consistency in pencil shading. Keeping pressure and stroke direction reasonably uniform distributes graphite evenly, producing a smoother and more controlled tone. Changing pressure on every stroke creates patchy marks, while repeatedly rotating the paper does not itself guarantee even coverage. An eraser removes graphite rather than building a tone. Therefore, option A is the useful habit, although stroke direction may be adjusted deliberately when describing form.