Which of the following groups of planets is termed as 'gas planets' as they are composed primarily of lighter ices, liquids and gases?

The correct answer is B, Jupiter, Uranus, Neptune, Saturn. These four outer planets are the gas planets, also called Jovian planets, made mostly of hydrogen, helium, ices and liquids rather than rock. The eight planets fall into two groups. The inner, or terrestrial, planets, Mercury, Venus, Earth and Mars, are small, dense and rocky, with solid surfaces. Beyond the asteroid belt lie the giant planets, which are huge, have low density, no solid surface, thick atmospheres, many moons and ring systems. Jupiter and Saturn are mostly hydrogen and helium and are called gas giants; Uranus and Neptune have more water, ammonia and methane ices and are sometimes called ice giants. Saturn is so light it would float in water. Option A is wrong because it includes Mars, a rocky terrestrial planet. Option C is wrong because it also includes Mars in place of Uranus. Option D is wrong because it includes Mars and leaves out Jupiter, the largest gas planet. Exam tip: Mercury, Venus, Earth and Mars are rocky; Jupiter, Saturn, Uranus and Neptune are gaseous Jovian planets.