The main source of downward convection flow in the mantle is called
ridge-pull
slab-pull
slab-push
ridge-push

The right option is; slab-pull

The main source of downward convection flow in the mantle is called slab pull.

Slab-pull is the force applied by a cold, dense oceanic plate descending into the mantle as a result of its own weight. This process is known as subduction. The oceanic plate has a density higher than that of the hotter mantle below it and the difference in their density causes the plate to submerge into the mantle.

rocks and weathering-matching

explanation:

for  example, forests have higher evapotranspiration than other ecosystems,  such  as grasslands, because of their deeper roots and greater leaf area. thus forests have a net moistening effect on the atmosphere and become a moisture source for downwind ecosystems.