Which word best describes the hot, weak, inner part of the upper mantle, which can flow? a. asthenosphere b. lithosphere c. crust d. core

Asthenosphere is the answer of this question. It best describes the all above mention properties. 

Asthenosphere is the the upper layer of the earth's mantle, below the lithosphere, in which there is relatively low resistance to plastic flow and convection is thought to occur.

Hi There!

Question - Which word best describes the hot, weak, inner part of the upper mantle, which can flow?

Answer - Asthenosphere

Why:

Lets check all the reasons in the question with the options.

Asthenosphere

Hot? Yes

Weak? Yes

Inner Part Of The upper Mantle? Yes

Flow? Yes

Lithosphere

Hot? Yes

Weak? No

Inner Part Of The upper Mantle? Yes

Flow? No

Crust

Hot? Yes

Weak? No

Inner Part Of The upper Mantle? Yes

Flow? No

Core

Hot? Yes

Weak? No

Inner Part Of The upper Mantle? I don't think so

Flow? No

Astheno sphere is the only choice that is all true in the question stated!

Hope This Helps :)