Answer:
D. magnetic polarity reversals
Explanation:
The marine magnetic anomalies are the result of two things; the seafloor spreading at the mid-ocean ridges and the magnetic polarity reversals.
The mid-ocean ridges are the places where the new crust forms. This places also have big influence on the magnetic anomalies, with the reason being that the magnetism has higher influence in this parts.
Also, the magnetic polarity reversals play a big role. The Earth has not always had the same magnetic polarity, and multiple times throughout its past the North and South Poles have been switching places when it comes to the magnetism.
The igneous rocks on the ocean floor have proof in them about this, as the metallic components are reacting to the magnetism and face toward the stronger magnetic field.
