What is most useful for painting several leaves of similar size with poster colour?

Correct answer: Maintain equal brush load and pressure

The governing concept is repeatable brush control. Keeping a similar amount of paint on the brush and applying similar pressure helps each stroke produce nearly the same width, coverage, and shape, making repeated leaves uniform. Using a different brush each time may change the mark, folding the paper does not control painted size, and adding more water can make the colour runny and the coverage inconsistent. Thus, maintaining equal brush load and pressure, option B, is most useful.