Option 1: Saturn. Regarding the duration of the year, Saturn takes approximately 29.5 Earth years to complete one orbit around the Sun. Therefore, it does not have the longest duration of the year among the given options.
Option 2: Jupiter. Jupiter takes approximately 11.9 Earth years to complete one orbit around the Sun. Therefore, it also does not have the longest duration of the year among the given options.
Option 3: Neptune. Neptune takes approximately 164.8 Earth years to complete one orbit around the Sun. This makes it the planet with the longest duration of the year among the given options. It takes a significantly longer time for Neptune to complete its orbit due to its large distance from the Sun.
Option 4: Earth. Earth takes approximately 365.25 days to complete one orbit around the Sun, which we consider as one year. Although Earth`s duration of the year is relatively short compared to Neptune, it is not the longest among the given options.
Therefore, the correct answer is Option 3: Neptune with the longest duration of the year.