Answer:
As one plate subducts, it sets up convection currents in the upper mantle that 'exert a net trenchward pull'
Explanation:
Rain and lightning would be the only two that commonly apply. I’d say lightning is the more dangerous of the two that this would be looking for without any other information on the assignment.
A coral is a type of Marine animal (Invertebrate) that secretes calcium carbonate to form an organic rock home.