What should be done to make the transition natural between a warm foreground and a cool middle ground?

Correct answer: Use neutral or mixed transitional colours between them

The governing concept is gradual colour transition and harmony in spatial composition. Warm foreground colours and cool middle-ground colours can look disconnected if they meet abruptly. Option A is correct because neutral or mixed transitional colours create an intermediate bridge, softening the temperature change and preserving depth. A thick black line creates a harsh division, while changing an entire area to blue or red removes the intended warm–cool relationship rather than integrating it.