Which colour is mixed with yellow to make yellow-green?

Correct answer: Green

The governing concept is the naming and formation of tertiary colours. Yellow-green is made by combining yellow, a primary colour, with green, the adjacent secondary colour. Thus option B is correct. Yellow mixed with orange would produce yellow-orange, not yellow-green; violet or red would create mixtures with different colour relationships. Reading the two parts of the compound colour name is the quickest valid method here.