Which mixture is required to make yellow-orange?

Correct answer: Yellow and orange

Yellow-orange is a tertiary colour formed by combining yellow, a primary colour, with orange, a neighbouring secondary colour. Therefore, option A gives the required mixture. Yellow and green would make yellow-green, while blue and violet make blue-violet. Red and green are complementary rather than an adjacent primary-secondary pair, so they generally produce a dull or neutral pigment mixture instead of the named tertiary colour. The colour-wheel relationship confirms the answer.