A population would be geographically isolated on an island.
Answer: Option A
Explanation:
A comparatively smaller piece of land that is not directly connected to any other bigger landmass because of being covered with water in all sides is referred to as an island. Without any means to cut the distance from over or below the water (ships, aircraft, submarines, etc.), it is impossible to reach or leave an island. Rivers and rain-forests seem to be comparatively more escapable or accessible.