Which proportion is correct for producing yellowish green?

Correct answer: More yellow and less blue

The governing concept is proportional colour mixing. Green is made by combining yellow and blue. If yellow is used in a greater proportion than blue, yellow dominates the mixture and shifts the hue toward yellow-green, so option A is correct. More blue would create bluish green, while equal amounts tend toward a more balanced green. Red is not the required component for producing yellowish green and could dull the mixture.