The plate boundary marked by deep-sea trenches, volcanic mountain chains, and severe earthquakes is the convergent plate boundary.

Here's why:

* Deep-sea trenches: These are formed when one tectonic plate subducts (slides) beneath another. The denser plate sinks into the mantle, creating a deep trench in the ocean floor.

* Volcanic mountain chains: As the subducting plate descends, it melts, generating magma that rises to the surface, often forming volcanic arcs along the edge of the overriding plate.

* Severe earthquakes: The friction and movement along the subduction zone cause intense earthquakes, some of which can be very powerful.

Let me know if you'd like to know more about convergent plate boundaries or other types of plate boundaries!