Marine magnetic anomalies can be used to estimate the

Marine magnetic anomalies can be used to estimate the rate of sea floor spreading.

Marine magnetic anomalies were first discovered in 1950 and they are described as the changes in earth's magnetic field due to the change of chemical composition of rocks. At mid-ocean ridges, the magnetic variation parallel to mid-ocean ridges supports seafloor spreading.  

The theory of seafloor spreading is proved by the presence of minerals present in gabbro and basalt rocks which depict magnetism properties resulting from the formation of ocean crust at ocean ridges. The rocks acquire magnetization after magma has risen and cooled. As the seafloor spread, the rocks are carried away from the ridges.

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the correct answer is c