The correct answer is (a.) one plate descends beneath another. Trenches form at sites where one plate descends beneath another. A trench is more like an excavation in the ground that is generally deeper than it is wide. It is generally used in battle formation, in which the front line is made of trenches.
The sea can act as a temperature regulator because it takes in heat energy in the summer but the land can’t do that (the suns rays are mostly reflected) so temperature isn’t kept as constant
