What is the most likely reason that there are no giant planets beyond Neptune?

Question

Answer

Any planet forming beyond Neptune's orbit would have been scattered outside of the solar system by gravitational encounters.

Answer

Any planets forming beyond Neptune would have drifted out of the solar system due to the weakness of the Sun's gravity at this distance.

Answer

There may be, but they would be so faint that astronomers have not found them yet.

Answer

By the time planetesimals grew to a large enough mass to hold onto an atmosphere, the solar nebula had been blown away.

Answer

There was no material to create planetesimals beyond the orbit of Neptune.

Crowdly