Question

which layer retains heat from the earths formation and is molten?
asthenosphere
lower mantle
outer core

Explanation:

The asthenosphere is a layer of the Earth that retains heat from the Earth's formation and is in a semi - molten state. The lower mantle is more solid compared to the asthenosphere. The outer core is also molten but it is mainly due to radioactive decay and not just heat from formation in the same context as the asthenosphere's description here.

Answer:

asthenosphere