What property was used as evidence to support seafloor spreading?

magnetism

sonar

density

boiling point

magnetism

Explanation:

Sea floor spreading talks about how the oceanic crust have been moving apart. The rate at which the oceanic crusts are drifting apart. One of the major evidence to back up sea floor spreading is magnetism.

Scientist found out that the rocks that makes up the ocean floor follows the pattern of magnetize stripe. Remember the rocks that makes up the ocean floor are majorly basaltic and it contains iron. The rocks formation are from the solidification of molten magma . As this magma cools to form rocks the iron contents align itself with the direction of the earth magmatic poles.

Note that the earth behaves like a magnet with the north and south pole respectively. The earth magnetic pole have been changing over time.  The changes affects the direction of this magnetic rocks on the ocean floor.    

b. the carbon cycle ensures living things have a source of hydrogen