What is the difference between adding white and black to a tertiary colour?

Correct answer: Adding white creates a tint, while adding black creates a shade

The governing concept is colour value modification. Adding white makes a tertiary colour lighter, and this lighter version is called a tint. Adding black makes it darker, and this darker version is called a shade. Hence option A gives both definitions correctly. Option B reverses them, while adding white or black does not increase saturation or change a tertiary colour into a primary colour.