What is suitable to add if a yellow-green mixture becomes too yellow?

Correct answer: A little green

Yellow-green is a mixture in which yellow and green are both visible. If it becomes too yellow, the governing principle is to increase the green component slightly. Add a little green, mix thoroughly, and check the colour before adding more. Red or orange can make the mixture dull or shift it toward warmer hues, while white mainly lightens the colour rather than correcting its yellow bias. Hence, option A is correct.