What is the main purpose of testing a sample before making an even red poster-colour background?

Correct answer: Check consistency dry value and brush-stroke result

The governing concept is preliminary testing for predictable application. A small sample reveals the mixture’s consistency, its value after drying, its coverage, and whether the chosen brush leaves acceptable strokes on the actual surface. Therefore option A is correct. Measuring paper length, checking brush price, or renaming the colour provides no evidence about how the red background will actually look or behave.