The answer is A: Core --> Mantle --> Crust.
Core: The earth's core is the center of the earth, which would ultimately be the deepest. The core is made up of alloy, which is a mixture of many medals, such as iron and nickel.
Mantle: The earth's mantle is the layer between the earths crust and core. Often made of silicate rocks.
Crust: The earth's crust is the outer-most of the three options. Usually made of up different types of rocks.
