Final answer:
No, the Earth's magnetic field is not parallel to the ground at all locations; it is parallel at the magnetic equator. The magnetic field strength is not the same globally; it is greatest at the magnetic poles, where the field lines are closest together.
Step-by-step explanation:
The Earth's magnetic field is not parallel to the ground at all locations. The direction of the field varies depending on where you are on Earth. At the magnetic equator, the field lines are more parallel to the surface, whereas they enter the Earth nearly perpendicularly at the magnetic poles. Additionally, the strength of the magnetic field is not uniform across the surface of the Earth. It is greatest at the magnetic poles and weakest at the magnetic equator. This is because the field lines are closer together (denser) at the poles, indicating a stronger field according to the principle that magnetic field strength is proportional to the closeness of the field lines.
If we consider the behavior of magnetic fields coming from a bar magnet as analogous, which possess field lines that are closer together near the poles indicating a stronger field, we can confirm that the Earth's magnetic field behaves similarly. It decreases in strength rapidly with distance away from the source (in this case, the Earth's core where the magnetic field originates).
Therefore, the correct answer to the given options is (c) The Earth's magnetic field is parallel only at the equator; its strength is greatest at the poles.