Which feature forms as a result of a tectonic plate boundary that creates an underwater mountain range in the open ocean?

The feature is a mid-oceanic ridge.

Explanation:

Tectonic plate is a massive, irregularly shaped slab of solid rock, that make up the earth's outer shell. It is also referred to as the lithospheric plate and has its major part under the ocean. Along its boundaries, some features are formed are: deep ocean trenches, volcanoes, island arcs, submarine mountain ranges, and fault.

The movements of the plates shapes the geological features of the earth. As a result of a tectonic plate boundary that creates an underwater mountain range in the open ocean, the feature that can be formed is the mid-oceanic ridge. A mid-oceanic ridge is an underwater mountain range that is formed by the movement of plate tectonics.

A mid-ocean ridge or mid-oceanic ridge is an underwater mountain range, formed by plate tectonics. This uplifting of the ocean floor occurs when convection currents rise in the mantle beneath the oceanic crust and create magma where two tectonic plates meet at a divergent boundary.