If adding white gives a colour a chalky, lifeless effect, which correction may be useful?

Correct answer: Add a small amount of the base colour back

The governing concept is controlled tinting: white raises value but can weaken saturation and make a colour look chalky. Adding a small amount of the original base colour restores hue strength and colour identity without making the mixture excessively dark. More white worsens the problem, much black changes the value sharply, and equal complementary colour may neutralise it. Therefore, option C is the practical correction.