Which tertiary colour contains the primary colour blue and the secondary colour green?

Correct answer: Blue-green

The governing concept is the naming and formation of tertiary colours. A tertiary colour combines two neighbouring colours, usually one primary and one secondary colour. Blue combined with green produces blue-green, so option A is correct. Yellow-green contains yellow and green, blue-violet contains blue and violet, and red-violet contains red and violet; therefore none of those alternatives contains the stated blue-and-green pair.