What Feature of Third Style Roman Mural Painting Distinguishes It

What feature of Third Style Roman mural painting distinguishes it from Second Style?

A) Third Style murals are much more concerned with figural representation than landscapes.
B) Third Style murals represent an attempt to imitate expensive colored marble instead of the natural world.
C) Third Style murals are independent motifs painted on the wall instead of vistas beyond the wall.
D) Third Style murals are completely flat and do not incorporate any sense of illusionistic space.