Which set of planets consists of the outer solar system?

The correct set of planets that represents the outer solar system includes Jupiter, Saturn, Uranus, and Neptune. These planets are referred to as the "gas giants" (Jupiter and Saturn) and "ice giants" (Uranus and Neptune) due to their compositions and distances from the Sun.

In the context of the solar system, the outer planets are distinguished by their larger sizes compared to the inner planets, their gaseous or icy compositions, and their greater distance from the Sun. Jupiter and Saturn are primarily composed of hydrogen and helium, while Uranus and Neptune contain a higher proportion of ices, such as water, ammonia, and methane in addition to hydrogen and helium.

The other options include planets that are either entirely within the inner solar system or contain a mix of inner and outer planets, which does not accurately represent the outer solar system. Thus, option C is the only set that correctly identifies all the outer planets, making it the correct answer.