Earth's outer core is than its inner core. a. solid; hotter b. solid; cooler c. liquid; hotter d. liquid; cooler

D

Explanation:

In general, the inner core of the earth is hotter than the outer core, even though the outer core is liquid and the inner core solid. The temperatures at the outer core range between 4000 – 5000 degrees centigrade while that of the inner core is about 5200 degrees centigrade. It is nonetheless important to note that the discontinuity between the two cores is actually the hottest region at about 6000 degrees. The inner core is solid (as compared to the liquid outer core) due to the enormous pressure at this region due to the weight of the overlying layers. This region experiences a pressure of approximately 3.6 million atmospheres (atm) keeping the iron from melting even though the temperature is way above the melting point of the metal.

the supermassive black hole is in the middle of the galaxy.