Which is the smallest planet in the solar system?

The answer is C. Neptune. Pluto was once considered the outermost planet, but it was reclassified as a dwarf planet in 2006. Neptune is the eighth and outermost planet in our solar system. It is a gas giant with a diameter of about 49,500 kilometers. Neptune is the fourth-largest planet in our solar system, after Jupiter, Saturn, and Uranus.

Explanation:

Pluto was once considered the outermost planet, but it was reclassified as a dwarf planet in 2006. This was because Pluto does not meet the criteria for a planet, which includes clearing the neighborhood around its orbit. Neptune, on the other hand, does meet the criteria for a planet, and it is the outermost planet in our solar system.