Which part of the mantle is still a solid but flows like a thick, heavy liquid asthenosphere core lithosphere crust

Option (a) is the correct answer.

Explanation :

The asthenosphere is a part of mantle. It is very viscous in nature. It flows and helps in moving the plates of earth.

Asthenosphere is weak ant it is the upper mantle of the Earth which ductilely deforms. This layer is present below the lithosphere at a depth between 80 and 200 km far below the surface.

Thus, we can conclude that asthenosphere is the part of the mantle that is still a solid but flows like a thick, heavy liquid.