Which choice is suitable for making a clean and vivid violet in acrylic colour?

Correct answer: Blue-biased red and red-biased blue

The governing concept is pigment bias in secondary-colour mixing. A vivid violet is made from a red that leans toward blue and a blue that leans toward red, because these pigments contain less unwanted yellow or green influence. Therefore option C is correct. Yellow-biased red mixed with green-biased blue tends to neutralise and dull the violet. Red plus green is complementary mixing, while yellow plus black cannot produce a clean violet.