What is the form produced by adding black to yellow-green called?

Correct answer: Shade

The governing concept is the distinction among tint, shade, and tone. Adding black makes a colour darker; the darker version is called a shade. Thus black plus yellow-green produces a shade, so option B is correct. A tint is made by adding white, and a tone is made by adding grey. A complementary colour is determined by a colour-wheel relationship, not by adding black.