Concept:The Earth is made up of concentric layers, and the innermost layer is the core.
Explanation:The Earth's interior is divided into the crust, the mantle, and the core.
The crust is the outermost layer, and the mantle lies beneath it.
The core is the deepest layer and is located at the very centre of the Earth.
Therefore, the innermost section is the core, not the sial, mantle, or crust.
Answer:D. core