Name a feature that is formed at a transform plate boundary.

At a transform plate boundary, tectonic plates slide past one another in a horizontal motion. This movement can create significant stress in the Earth's crust, which is released in the form of earthquakes. The friction between the plates can also result in distinct fault lines, where the ground is visibly displaced along the boundary of the plates. These features are characteristic of transform boundaries and illustrate the dynamic nature of Earth's lithosphere as it adjusts continuously to tectonic movement.

In contrast, the other options represent features associated with different types of plate boundaries. Volcanic islands and mid-ocean ridges are formed primarily at convergent or divergent boundaries, where subduction or seafloor spreading occurs, leading to volcanic activity and the creation of new crust. Mountain ranges typically form at convergent boundaries where two continental plates collide, resulting in uplift and folding of the Earth's crust. Thus, the occurrence of earthquakes and fault lines is the defining characteristic of transform plate boundaries.