Explanation:

Population density is calculated as the number of people per square kilometer. The general ranking of the given regions in terms of increasing population density is:

1. Oceania (A) - Lowest
   • Oceania has vast land areas like Australia with very low population density (~5 people per km²).
2. North America (C)
   • The U.S. and Canada have large landmasses but relatively lower population densities compared to Africa and Europe (~25 people per km²).
3. Africa (B)
   • Africa has higher population densities, especially in regions like Nigeria and Egypt (~50 people per km²).
4. Europe (D) - Highest
   • Europe is the most densely populated of these regions, with small land areas and high urban concentration (~72 people per km²).

Thus, the correct sequence from low to high population density is:
? Oceania (A) → North America (C) → Africa (B) → Europe (D)

Correct answer:
? B) A, C, B, D