What is the correct colour-wheel position of red-violet?

Correct answer: Between violet and red

The governing concept is that a tertiary colour is placed between the two colours named in its compound name. Red-violet is made from red and violet, so its correct position is between red and violet on the colour wheel. Blue-green belongs between blue and green, yellow-orange belongs between yellow and orange, and yellow-green belongs between yellow and green. Thus option D is the only correct placement.