Final answer:
Population clusters in Canada and the United States are mainly found along coasts and inland waterways, including areas like Vancouver and the Great Lakes region.
Step-by-step explanation:
Population clusters in Canada and the United States are primarily located along the coasts and inland waterways. These areas offer access to trade routes, resources, and have historically been centers of industry and commerce. Cities like Vancouver, located on the coast in British Columbia, act as major ports and facilitate trade with the Pacific Rim. The Great Lakes region is another area of dense population, being historically important for manufacturing due to proximity to both labor reserves and markets for manufactured goods, as well as having access to essential raw materials like iron ore and coal. As a result, the correct answer to the question would be: b) along the coasts and inland waterways.