Final answer:
The statement is true as oceanic crust sinks into the mantle at deep-sea trenches.
Step-by-step explanation:
The statement 'At a deep-sea trench, oceanic crust sinks into the mantle.' is True.
Deep-sea trenches are long, narrow depressions on the ocean floor. They are formed when tectonic plates converge, and one plate, usually the denser oceanic plate, subducts beneath the other.
As the oceanic crust sinks into the mantle, it creates a subduction zone where volcanic activity may occur. This process is a key component of plate tectonics and helps explain the formation of features like island arcs and mountain ranges.
Learn more about Plate Tectonics