In the video this question was provided for, you should be able to find the passage, "The lithosphere is a rigid shell made up of plates. In order to understand what the plates are like, imagine taking a hard-boiled egg and cracking it all over. Do not peel it; just crack it. It is still all together on the outside of the egg, but it is broken into "plates." The plates of the lithosphere move slowly about on the plastic, formless asthenosphere beneath."
Answer: Lithosphere