Identify the nearest planet from the Sun.

Concept: All eight planets orbit the Sun at steadily increasing average distances. Counting outward from the Sun the order is Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus and Neptune, so the innermost planet — the one with the smallest orbital radius — is the nearest to the Sun.

Application: Among the planets offered here, Mercury has the smallest average orbital distance, about 57.9 million km (0.39 AU) from the Sun, which makes it the innermost planet of the Solar System.

Cross-check: Mars, Jupiter and Neptune all orbit far beyond Mercury, so Mercury is unambiguously the planet nearest to the Sun.