E.) Mesosphere, Asthenosphere, Outer layer Unfortunately there is no standard terminology for three mantle layers. <span>I can be sure that "ionosphere" and "thermosphere" refer </span> <span>only to atmospheric layers, so you can rule out A, B, and D. </span> <span>"Mesosphere" may be used to refer to an atmospheric layer, </span> <span>but is also often used to refer to a mantle layer. </span>
<span> , </span> <span>so I'll go with E even though I don't like it much. </span> <span>I guess what is meant by "outer layer" is the part of the lithosphere </span> <span>that does not match crustal composition.</span>
