Question

tectonic plates slide around like slow motion bumper cars on the ____________, which is part of the mantle. lithosphere asthenosphere mantle

Explanation:

The asthenosphere is a semi - fluid layer in the upper mantle. Tectonic plates (which are part of the lithosphere) move over the asthenosphere. The lithosphere is rigid and consists of the crust and upper mantle. The mantle is a larger layer. Since the question says "which is part of the mantle" and tectonic plates move over it, the asthenosphere is the correct answer.

Answer:

asthenosphere