Which of the following has not yet been discovered?

• A. An exoplanet that is truly Earth-like with liquid water
• B. An exoplanet with multiple moons
• C. A planet larger than Jupiter
• D. A planet orbiting a binary star

Answer: (A)

Exoplanet discoveries show a range of outcomes, and this item focuses on what has actually been confirmed. We have confirmed planets that are larger than Jupiter and we’ve found planets that orbit binary stars, so those kinds of planetary configurations do exist. Evidence for moons around exoplanets is an active area of research, with some intriguing signals but not as solidly established as the giant planets or circumbinary planets.

But a truly Earth-like planet with surface liquid water has not yet been confirmed. While many rocky planets in or near the habitable zone have been found, proving the presence of liquid water on the surface requires conditions and evidence we haven’t definitively obtained yet. We can infer possible atmospheres and temperatures, but direct confirmation of surface oceans remains out of reach with current methods. That’s why this option is the best answer.