An artist uses red red-orange and orange in sequence. Which principle does this demonstrate?

Correct answer: Adjacent colour transition

The governing concept is an adjacent or analogous colour progression. Red-orange lies between red and orange on the colour wheel, so the sequence red → red-orange → orange creates a gradual transition with related hues; option A is correct. Complementary contrast would require colours from opposite regions, not neighbouring ones. The sequence is neither neutral nor unrelated because all three colours belong to the same nearby warm range.