Final answer:
J. Tuzo Wilson confirmed Alfred Wegener's idea that continents were once connected by discovering that the Atlantic Ocean opens and closes over time, supporting the theory of plate tectonics.
Step-by-step explanation:
J. Tuzo Wilson's discovery that confirmed Alfred Wegener's idea that the continents had once been connected was the discovery that the Atlantic Ocean opens and closes repeatedly over time, which is indicative of the process of horizontal tectonic plate movement that supports continental drift. This discovery was a significant step in the development of the theory of plate tectonics, which provided the mechanism for Wegener's earlier theory of continental drift.
Wilson's work showed how the Earth's continents not only fit together like pieces in a puzzle due to their matching coastlines, but also how they physically move apart and come back together over geological timescales, further reinforcing Wegener's concept of a past supercontinent, Pangaea.