What happens when yellow is greater in yellow-orange?

Correct answer: The colour will shift toward yellow

Yellow-orange is a tertiary colour between yellow and orange. Increasing the amount of yellow makes the mixture visually closer to yellow, so option A is correct. It does not automatically become pure orange, because the proportion of yellow has increased rather than disappeared. A red-orange shift would require stronger red influence, and the mixture would not change to green without different pigments.