Which combined control is most important for making a long curved line of uniform thickness with a liner brush?

Correct answer: Even pressure, continuous speed, and sufficient paint flow

Uniform line quality depends on three linked controls: steady pressure, a continuous movement, and enough paint flowing through the liner. Together they keep the brush point flexing consistently and prevent gaps or thick spots, so option A is correct. Heavy pressure, dry paint, pauses, or brush size alone cannot guarantee an even curved line.