What can be done to make orange more realistic in a sunset painting?

Correct answer: Vary the ratio of red and yellow

The governing concept is colour mixing and variation. Orange is produced by combining red and yellow, and changing their proportion creates warmer, redder or yellower versions suited to different parts of a sunset. Using one identical orange ignores changes in light and atmosphere. A large amount of blue would dull or neutralise the orange rather than make it naturally varied, and blackening every area removes the sunset’s light. Thus A is correct.