Answer:
See Below
Step-by-step explanation:
Reason 1: Some planets, like Uranus are farther from the sun, and thus have a longer orbit, or planets closer to the sun, like mercury, have such a short year because they are so close to the sun.
Reason 2: The sun's gravitational pull is stronger on planets closer to it then farther, which is why Mercury has such a short year in comparison to Earth or Uranus.