Which simple exercise is useful for practising blending?

Correct answer: Blend two colour bands in the middle

The governing skill is creating a smooth transition between neighbouring colours. Drawing two colour bands and gradually merging them in the middle gives direct practice in controlling pressure, paint quantity, and brush movement. Thus, option A is correct. Cutting paper, leaving a brush in water, and sharpening a pencil may be useful in other situations, but none of them develops the blending action itself. The exercise can be repeated with light and dark versions of related colours.