Final answer:
Earth years are shorter than Saturn years, as the distance from the Sun dictates orbital periods according to Kepler's laws, with Earth completing its orbit in just over 365 days and Saturn taking about 30 years.
Step-by-step explanation:
Based on planetary orbits alone, the comparison that is most likely correct is that Earth years are shorter than Saturn years. Planetary orbits are defined by Kepler's laws, which tell us that the farther a planet is from the Sun, the longer it takes to complete one orbit. Earth is 1 AU (Astronomical Unit) from the Sun and takes a little more than 365 days to orbit the Sun, whereas Saturn is about 10 AU from the Sun and takes nearly 30 years to complete one orbit. Therefore, it is clear that an Earth year is significantly shorter than a Saturn year.
Mars being denser than Neptune is not the most likely comparison since Neptune, despite its larger volume, is still significantly more massive than Mars. Venus does have a smaller tilt than Uranus, which is true, but this comparison is less about the planetary orbits and more about rotational tilt. Lastly, Jupiter does indeed have shorter days than Mercury; Jupiter's rotation period is 10 hours compared to Mercury's longer rotation period. However, this comparison is about the length of days based on the planets' rotation and not their orbits.