Computer Simulations of the Formation of the Solar System Show

Computer simulations of the formation of the solar system show that the material in the vicinity of the asteroid belt is not NOT in the form of one large planet because:

A) most of the material originally in the asteroid belt crashed into Mars, creating the heavily cratered terrain we see there.
B) a violent collision destroyed two proto-planets, the debris from of became the asteroid belt.
C) this region is where the gravitational field of the Sun is balanced by that of Jupiter, preventing coalescence of matter into a planet.
D) Jupiter''s gravitational pull flung most of the material in this region out of the solar system and prevented coalescence of the rest.