What allows the asthenosphere to be able to move slowly?
a. the heat of earth's interior at that depth
b. the friction of the plates moving above it
c. the magma moving up from earth's inner core
d. the pressure of the rock above the asthenosphere

Option (A)

Explanation:

The asthenosphere is the upper part of the mantle and this region is just below the lithosphere. The lithospheric plates are divided into 2 types, namely the continental crust and the oceanic crust. These plates moves over this layer of asthenosphere due to the generation of the convection current in the mantle. This currents also forces the asthenosphere to move considerably at a slower rate. This convection current is formed due to the heat radiated from the core (interior) of the earth. The core of the earth is comprised of the denser and molten rocks such as iron and nickel. The rocks in the asthenosphere are solid in nature, but they have the ability to move during deformation.

Hence, the correct answer is option (A).