My first instinct was a very simple category. Seeing 'River' and 'Mountain' together made me think of 'Landforms' or 'Geographical Features'. It felt solid, classic, and direct. I was confident this was the key.
Then Forest appeared. While a forest is a geographical feature, the word felt different, more biological than a pure landform. My 'Landforms' theory started to creak. When Desert and Ocean followed in quick succession, the theory completely shattered. The category was too academic and restrictive. *Wait*, I thought, *what is the most basic way to describe all five of these things?* I abandoned the scientific terms and tried to think like an artist or a poet describing the world. The idea that clicked was about fundamental, large-scale parts of the Earth's surface.
- River → Natural landscape: a flowing body of water, a major aquatic feature.
- Mountain → Natural landscape: a large landform that rises prominently above its surroundings.
- Forest → Natural landscape: a large area dominated by trees and other woody vegetation.
- Desert → Natural landscape: a barren or arid area with minimal precipitation.
- Ocean → Natural landscape: the vast body of saltwater that covers most of the Earth.
Once I hit on 'Natural landscapes', everything snapped into place. The remaining clues weren't just confirming the theme; they were perfect, definitive examples of it. The solution was simple, elegant, and hiding in plain sight the entire time.