Question

question 1-21
this is the mostly solid layer of earth that is highly viscous where the driving force of plate movement comes from.
inner core
crust
outer core
mantle

Explanation:

The mantle is a mostly - solid, highly viscous layer. Convection currents in the mantle drive plate movement. The inner core is solid iron - nickel. The crust is the thin, outermost layer. The outer core is liquid iron - nickel.

Answer:

D. Mantle