What is required for an ocean trench to form

Trenches are the V-shaped depression that are formed in the ocean when two distinct plates collides with one another, of which the denser plate (oceanic plate) gets subducted beneath the less denser plate (continental/oceanic plate), creating a subduction zone or the benioff zone.

      Due to this subduction phenomenon, the V-shaped depression forms in the ocean which is known as the trench.

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explanation:

b. the carbon cycle ensures living things have a source of hydrogen