Other than the Niagara Bar, where is Lake Ontario free of shoals?

The Northeast corner of Lake Ontario is generally free of shoals, making it the correct choice. This region features deeper waters and is characterized by a lack of shallow areas compared to other parts of the lake. The geography and water depth in the Northeast corner facilitate safer navigation, unlike areas with more pronounced shoals and underwater hazards.

The Southeast shore, for instance, has some shallow regions and potential navigational challenges. Similarly, the Hamilton area is not as prominent for deeper water and contains places that could be considered hazardous for navigation due to shoals. The Toronto to Cobourg coast, while having some navigational features, also includes shallow areas that could pose risks to vessels. All these factors combined reinforce why the Northeast corner is recognized for being relatively shoal-free compared to the other options.