Which statement defines a natural boundary?

• A. A geometric boundary is defined by straight lines independent of physical features; Example: 49th parallel north.
• B. A boundary defined by physical geography such as rivers or mountains; Examples: Rio Grande and the Andes.
• C. A boundary drawn to accommodate religious division.
• D. A boundary that marks economic zones.

Answer: (B)

Natural boundaries arise from the physical geography of a region, so the border follows a land feature like a river, mountain range, or desert. The Rio Grande and the Andes exemplify this because the boundary aligns with water or rugged terrain, naturally shaping how land is divided. In contrast, a line drawn straight across the map ignores terrain, and boundaries based on religion or economics are human-made divisions rather than features of the landscape.