<u>Answer and Explanation:</u>
The mechanism which is responsible for moving the plates that bring change in the position of the continents is the convection in the asthenosphere.
Henry Hess, a geologist and an American Navy officer in the World War II, discovered that the sea floor and the the Mid Atlantic Ridge is spreading which helped the the scientists in studying and understanding the mechanism of how the plates move.
The pressure on the inner core is greater than on the outer core and the melting point of iron, and because the pressure effect is higher than the temperature effect, the inner core is solidified.
The correct answer is D. Steel
