Rocks become magnetic when ; ( D ) Iron particles within the rock align with Earth's magnetic field.
The magnetic components of the earth are the iron particles which are components of a rock and the Earth's core which is an in-movable part of the earth's crust.
Therefore for a rock to become magnetic its iron particles have to come in contact/ align with the magnetic field within the Earth.
Heating up the rocks will increase its' temperature and increase the possibility of producing molten magma and not making the rock magnetic.
Hence In Conclusion Rocks become magnetic when iron particles within the rock align with Earth's magnetic field.
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