Which planets are classified as gas giants?

• A. Mercury, Venus, Earth, Mars
• B. Jupiter, Saturn, Uranus, Neptune
• C. Earth, Mars, Venus, Mercury
• D. Pluto and Eris

Answer: (B)

Gas giants are the large planets with thick atmospheres dominated by hydrogen and helium and with little solid surface. In our solar system, that describes the outer four planets: Jupiter, Saturn, Uranus, and Neptune. They are enormous compared with the rocky, close-in planets and are mainly gaseous (with ices contributing to their outer makeup in the case of the farthest two). The other options include rocky terrestrial planets (Mercury, Venus, Earth, Mars) or dwarf planets (Pluto and Eris), which are not gas giants.