if scientist were to watch a planet for millions of years and see no movement on the crust, it might indicate that the planet has no what?

It indicate that the planet has no gravitational pull

a. convection below the crust

Explanation:

It would indicate that the planet has no motion or movement beneath the layer of the crust as the tectonic plates that form the rocks are themselves absence of this show state the composition of the planet is different to that of the terrestrial and the gases against and that is different from the tiny dwarfs. As the earth has various convective current that originates at its base and these are responsible for the geomagnetic properties of the planet and the formation of the hard and dense core of the earth is itself a fact of the high density of the metallic components.