Final answer:
The differently oriented magnetic bands of rock on the ocean floor are due to seafloor spreading by plate tectonics and the Earth's magnetic field reversals. The spreading rate and coordinated reversals in magnetization can be used to give the historical record of the Earth's magnetic field. Hence the correct answer is option A
Step-by-step explanation:
The differently oriented magnetic bands of rock on the ocean floor are primarily due to seafloor spreading by plate tectonics and the Earth's magnetic field reversals.
Seafloor spreading occurs at mid-ocean ridges, where new oceanic crust is formed as tectonic plates move apart. As magma rises and solidifies, it aligns with the Earth's magnetic field at the time. Over time, the Earth's magnetic field reverses, causing rocks formed at different times to have different magnetic orientations.
This knowledge of the spreading rate and the coordinated reversals in magnetization can be used to give the historical record of the Earth's magnetic field. By studying the magnetic bands on the ocean floor and dating the rocks, scientists can determine the ages of the reversals and provide insights into the Earth's magnetic history.
Hence the correct answer is option A