Which statement describes one event that happens at deep-ocean trenches?

Question

Crust is formed.
Mountains are formed.
Seafloor spreading occurs.
Denser plates slide under lighter plates.

Answer 1

The statement that describes one event that happens at deep-ocean trenches is: Denser plates slide under lighter plates.

This process is known as subduction, where an oceanic plate (which is denser) is forced beneath a continental plate (which is lighter) or another oceanic plate, leading to the formation of deep-ocean trenches.