What is formed by adding black to a secondary colour?

Correct answer: A darker shade of that colour

Adding black to a secondary colour lowers its lightness and creates a darker version called a shade. For example, adding black to green produces a darker green. This process does not create white, a primary colour, or a complementary colour, because those are different colour results requiring different pigments or relationships. In contrast, adding white creates a tint, so option A correctly describes the effect.