Which technique is useful for making a thin curved line with poster colour?

Correct answer: Use a thin brush with light even pressure

The governing concept is brush control: line width depends mainly on the brush size, its angle, and the pressure applied. A thin brush with light, even pressure allows the artist to guide a smooth curve without spreading too much paint. Therefore, option C is correct. Pressing the whole brush produces a wider mark, thick paint reduces control, and dipping the paper in water does not create a controlled painted line. Practising the curve slowly improves accuracy.