Beyond the petition Neptune a field of smaller bodies orbits the Sun. Some scientists think these objects are the remains of material that formed the early solar systems. Use what you know about how solar systems form to evaluate this hypothesis.

This is a very valid hypothesis for many reasons. One is that solar systems form from massive amounts of dust, ice, and debris that eventually form into planets and such. This means it is very possible for this 'excess material' if you will to have moved into orbit behind Neptune.