Which tertiary colour lies approximately opposite yellow-green on the colour wheel?

Correct answer: Red-violet

The governing concept is complementary opposition on a twelve-part colour wheel. Yellow-green lies on the yellow-to-green side of the wheel; the region approximately across from it is red-violet. Therefore option D is correct. Red-orange and yellow-orange are located near yellow and orange, while blue-green is near green and blue, so those choices are not opposite yellow-green even though they are also tertiary colours.