The evidence for the existence of Earth’s magnetic field from the options you provided is:
Mid-ocean ridges having iron that is turned in different directions.
This phenomenon is related to the process of seafloor spreading and the magnetic stripes on either side of mid-ocean ridges, which record the Earth's magnetic field reversals over time. The alignment of iron minerals in these rocks reflects the direction of the magnetic field when they solidified, providing strong evidence of the magnetic field's presence and its reversals.