Step 1: Analyze the factors affecting population density. High population density is generally found in regions with favorable climates, fertile land, abundant water, and a high level of economic development.
Step 2: Evaluate the given regions.
Western Europe: Has a temperate climate, fertile soils, abundant resources, and is highly industrialized and urbanized. It is one of the most densely populated regions in the world.
Equatorial region: Characterized by hot, humid climates and dense rainforests, making large-scale settlement difficult.
Desert region: Extreme heat and lack of water make these regions sparsely populated.
Polar region: Extreme cold and ice cover make these regions largely uninhabitable.
Step 3: Conclude based on the analysis. Western Europe is the only region among the options that is densely populated.