Answer:
D.very slowly (centuries to a million years) when it forms a deep pluton.
Explanation:
Magma is a molten rock that forms within the earth crust. It is sometimes called melt. When it reaches the earth surface, it is called lava.
Only D is correct. Magma would cool slowly in a very deep pluton. In such an enviroment, access to circulating ground water is cut off and the temperature would be close to that by which the melt forms.
When magma cools and solidifies, it forms a wide variety of igneous rocks.
In the presence of circulating ground water, magma would cool and crystallize very rapidly. The ground water would provide more fluid phase for the movement of ions within the very thick and viscous melt thereby facilitating crystallization of minerals in the melt. Due to the temperature of the water, it serves as a coolant for the melt. The ground water takes heat away and returns with a more cold water.
Magma cools faster if the surface area of the intrusion is very large. A larger surface area would help more heat to dissipate and leave the body of the melt.
