Concept:Population density measures how many people live in a unit area, typically a square kilometre. Explanation:Population density is calculated as the total population divided by the total land area. It is stated as the number of people per square kilometre. This measure helps compare how crowded or sparse different regions are. Option A (people per house) refers to household size. Option C (people per village) refers to settlement size. Option D (people per family) refers to family size. None of these measure the concentration of people over a land area. Only “people per square kilometre” correctly matches the definition of population density. Answer:Option B: People per square kilometre