First off, option B. is out of the answer, because a trench is absolutely not a plate boundary. Although, a trench may form from the disturbance of two convergent plates colliding, with one of the converging plates moving beneath the other, which is known as subduction.
Anyways, mountain ranges occur at convergent boundaries. Movement of tectonic plates create volcanoes. The volcanoes erupt and form mountains.
In short, your answer is C. Convergent.
Faith xoxo