Overfishing is the main factor because removing far more fish than the population can replace each year erodes the breeding stock until it can no longer sustain the fishery. On the West Coast, intense harvesting during key migration and spawning periods, often with limited controls, meant stocks declined faster than they could recover, leading to a collapse. Climate or natural changes can influence fish runs, but they don’t automatically cause collapse unless fishing pressure is already high. While better fishing technology can speed up catches, it amplifies the impact of overfishing when not matched with strong management and conservation limits. A lack of a salmon treaty speaks to governance, but the ecological trigger of the collapse is the excessive harvest.

Access to transportation shapes where and how cities grow. When a place has reliable ways to move people and goods—by road, rail, or air—it becomes easier for businesses to operate, for workers to commute, and for goods to be shipped. That accessibility draws people and economic activity to areas around these hubs, so urban development concentrates near airports, train stations, and major highway intersections. In Canada, this shows up as cities expanding along key corridors and building dense cores around transit hubs, ports, and airports, with transportation networks continually evolving to meet growth. Public transit, in particular, helps manage crowded central areas by offering efficient alternatives to car travel, supporting higher-density development without unbearable congestion. The idea that urban areas grow away from networks, or that networks only expand after growth, or that growth has no relation to transportation, doesn’t fit how Canadian cities actually develop. The relationship is a reinforcing cycle: better transportation attracts growth, and more growth, in turn, spurs further investment in transportation.

Biological water pollution is about contamination of water with living organisms that can cause disease or disrupt ecosystems. The option describing bacteria and viruses in the water best fits this idea because these are living microorganisms that directly threaten health and aquatic life when they are present. They require treatment methods like disinfection to protect drinking water and recreational use. Pesticides are chemicals, not living organisms, so they fall under chemical pollution. Metal ions from pipes are also chemical contaminants, usually from corrosion or runoff. Sunlight exposure isn’t a contaminant itself; while it can influence water chemistry and biological growth, it’s not pollution by living organisms.

Think about how geographers describe where things are and what they mean. The main idea here is that place is about the meanings, identity, and character of a location—what makes it feel special or important to people—while space is about how things are arranged across the land—the patterns of where people live and where industries and resources are located. So the best statement says place refers to the meanings and identity of places, and space refers to the distribution of population and industries. That captures the two distinct ideas clearly: place is about what a location represents to people, its culture and history, and space is about how populations and economic activities are spread out across Canada. Other descriptions mix these ideas with things like just the physical location, maps, climate, or time zones, which don’t accurately separate the symbolic, human-side nature of place from the spatial, distribution-focused nature of space.