b=Along with the spin of the Earth, what causes its magnetic field? the movement of molten rock in the outer core the use of compasses on the surface of the Earth the presence of magnetic rock layers in the lithosphere the partially melted rocks of the asthenosphere

It is probably from the presence of magnetic rock layers in the lithosphere. Prety much because that means the earth will be magnetic.

The correct answer is the movement of molten rock in the outer core.

Explanation:

Inside the Earth is the inner core, which is solid. The temperatures found here are incredibly high, so much so that they can't even be measured. Surrounding this core, is the outer core. Here the material is liquid which allows it to flow.

There are differences in pressure and temperatures between one core and the other and this causes convection currents to be formed that carry the molten iron inside.

Given that Earth's magnetic poles move, and that the flowing iron is a conductor of electricity, a magnetic field inevitably forms.

This is a continuous circuit where molten material moves and creates its own energy constantly. And the magnetic field they generate is the one that envelops the planet.