Every 100,000 to 200,000 years, the magnetic poles of Earth reverse. Rocks that contain iron provide a record of both normal and reversed magnetic poles. The pattern of normal and reversed magnetic poles as recorded in the rock on either side of the Mid-Atlantic Ridge provide evidence supporting the Theory of Plate Tectonics because - a
the composition of the rock changed every time the plates pushed against each other.
b
the symmetric pattern shows where plates are moving away from each other.
c
deposits of iron in the rock were only made when the plates stopped moving.
d
the bands of rock showing normal and reversed poles are not all the same width."