Option 1 states that Neptune ranks first in our Solar System in terms of size. This is incorrect as Neptune is not the largest planet.

Option 2 states that Neptune ranks second in our Solar System in terms of size. This is also incorrect as there is at least one planet larger than Neptune.

Option 3 states that Neptune ranks third in our Solar System in terms of size. This is again incorrect as there are at least two planets larger than Neptune.

Option 4 states that Neptune ranks fourth in our Solar System in terms of size. This is the correct answer as there are three planets larger than Neptune - Jupiter, Saturn, and Uranus.

Therefore, the answer provided (option 4) is correct.