When molten material hardens into rock on the ocean floor, the domains of the iron it contains a. disappear. b. line up in the direction of earth’s magnetic field. c. point in random directions. d. never become magnetic.

Option B. line up in the direction of Earth’s magnetic field.

Explanation:

In a molten rock, traces of iron found align themselves in the direction of earth’s magnetic field. This happens because each tiny particle of iron in the molten rock act as a small magnet with magnetic north and south poles. These poles re-orient themselves as per the direction of earth’s magnetic field. This happens till the rock is in molten stage, once it gets solidified the minute magnets gets stable in one orientation.

Hence, option B is correct.