Which canal connects Lake Ontario to the upper Lakes?

The Welland Canal is the key connection between Lake Ontario and the upper Great Lakes, such as Lake Erie. It allows vessels to bypass the Niagara Falls, a major natural barrier, by providing a navigable route that is crucial for shipping and transportation. This canal facilitates the movement of goods between these significant bodies of water, making it an essential component of the Great Lakes navigation system.

The other options do not serve this function. The Niagara River flows between Lake Ontario and Lake Erie but does not provide a direct navigable channel for large vessels, especially due to the falls. The Erie River is not a relevant connection, as it does not link Lake Ontario to the upper lakes. The Grand River, while a river in Ontario, does not connect to any of the Great Lakes directly and is not part of the transportation network that links these major waterways. Thus, the Welland Canal is the most logical and accurate choice for connecting Lake Ontario to the upper Great Lakes.