What Influence Did Jupiter Have on the Formation of the Asteroid

What influence did Jupiter have on the formation of the asteroid belt, and how do we know?

A) We have watched other solar systems in their early stages of formation. They show Jupiter-size planets clearing out much of their asteroid belts.
B) Computer simulations have shown that in the absence of a Jupiter-size planet, an Earth-size planet would have formed in the asteroid belt.
C) Computer simulations have shown that a Jupiter-size planet has no influence on the formation of the asteroid belt.
D) We have watched other solar systems in their early stages of formation. They show that Jupiter-size planets have no influence on the formation of an asteroid belt.