Question

this layer heats up the mantle.
a crust
b lithosphere
c asthenosphere
d core

Explanation:

The core is the innermost layer of the Earth. It is extremely hot due to radioactive decay and residual heat from the Earth's formation. This heat is transferred outward, and one of the layers it affects is the mantle. The crust is the outermost layer and is cooler. The lithosphere includes the crust and the uppermost rigid part of the mantle. The asthenosphere is a semi - fluid layer within the mantle. So, the core is the layer that heats up the mantle.

Answer:

d. Core