Which statement best defines a habitable world?

• A. Has conditions suitable for life
• B. Is Earth-like in appearance
• C. Receives energy from a nearby star only
• D. Has abundant oxygen in its atmosphere

Answer: (A)

A habitable world means a place that has conditions that could support life as we know it—not just how it looks, but whether the environment could sustain living organisms over time. This includes factors like the presence of liquid water, a available energy source, and a climate and chemistry that can support metabolism and stability. Because of that, the broad idea is about suitability for life in general, rather than surface appearance, a single energy source, or a specific atmospheric gas.

Thus, having conditions suitable for life is the best description. Being Earth-like in appearance isn’t required, since many potential habitats might look very different. Receiving energy from a nearby star isn’t the only way a planet could maintain life-supporting conditions (internal heat or tidal heating can contribute too). Abundant oxygen in the atmosphere isn’t a universal requirement for life—many life-supporting environments could have little or no free oxygen.