Question

this is a major river which flows into the great lakes and creates a vital seaway that keeps canada interconnected. st. lawrence river hudson river mississippi river niagara falls

Explanation:

The St. Lawrence River flows into the Great Lakes and forms the St. Lawrence Seaway, which is crucial for Canada's connectivity. The Hudson River is in the northeastern United States. The Mississippi River is in the central United States. Niagara Falls is a waterfall, not a river that flows into the Great Lakes to form a seaway.

Answer:

St. Lawrence River