Which image best illustrates the magma convection currents within earths interior

The correct image is image in the bottom left.

Explanation:

Convection is the heat transfer due to bulk movement of  molecules within a fluids like: gas . liquids. The current which results from the convection are termed as convection currents.

Convection currents are found in earths mantle. Heated mantle or magma (molten rocks) rises from deep inside the mantle and cooled mantle flows down. This cyclic movement of magma creates convection current within earth interiors.

So, the image at bottom left is correct illustration of magma convection currents within earths interior.