Which observed feature of the outer planets contributes most directly to reducing destabilizing gravitational interactions between them?

The outer planets are separated by large distances, so the gravitational pull each exerts on its neighbors is weaker than it would be if they were closer together. This reduces the chance of destabilizing interactions. The correct choice is “Their orbits are spaced far apart”; rings, shared orbital direction, and moon rotation do not reduce planet-to-planet gravitational interactions as directly.

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