Which mixture is used to make red-violet?

Correct answer: Red and violet

The governing concept is tertiary-colour formation through mixing neighbouring hues. Red-violet lies between red and violet on the colour wheel, so combining red, a primary colour, with violet, an adjacent secondary colour, gives red-violet. Option A is therefore correct. Yellow-orange, blue-green, and yellow-green are also tertiary hues, but they arise from the different pairs shown in the other options.