C is the answer to this question. The mantle is known to be in between the core and the crust of the earth. There are also different planets that come with their own mantle. The mantle may sometimes be made of rock or ice. On Earth, the mantle is made of rock and is considered to be very large.
The rock layer is made out of different minerals such as magnesium, iron, and calcium. There are also other elements that can be found there. The layer of the mantle is definitely thicker than the crust and even bigger than the core. The fact that the convection currents can be found here makes sense.