Final answer:
The Mackenzie River is the largest and longest river in Canada and is the second largest river in North America. It flows from the Great Slave Lake and drains into the Arctic Ocean.
Step-by-step explanation:
The largest and longest river in Canada is the Mackenzie River. It is also the second largest river in North America, after the Mississippi River. The Mackenzie River flows through Canada's northwestern territories, originating from the Great Slave Lake in the Northwest Territories and flowing into the Arctic Ocean. It is a massive waterway that plays a crucial part in the drainage system of the western part of the Canadian Shield.