A dark green mixture was lightened but began to look chalky. What is the likely cause?

Correct answer: Too much white was added

The governing concept is the effect of white on value and saturation. White raises the value of green, but adding too much can reduce its chromatic intensity and make the mixture appear opaque, pale, and chalky. Therefore, option A is correct. More blue would normally shift the hue toward blue, red would neutralise or warm it, and excess water generally thins paint or increases transparency rather than creating a chalk-like body. White should be added in small increments.