Final answer:
Ceres is the only dwarf planet not classified as a Trans-Neptunian Object, and it is also the largest known asteroid with a diameter of about 940 km.
Step-by-step explanation:
The only dwarf planet that is not a Trans-Neptunian Object (TNO) and is also the largest known asteroid with a diameter of about 940 km is Ceres. Initially classified as a planet upon discovery, Ceres was later deemed an asteroid before being reclassified once again as a dwarf planet. Unlike other dwarfs such as Pluto, Makemake, and Haumea, which reside in the Kuiper Belt beyond Neptune, Ceres is located in the asteroid belt between Mars and Jupiter, making it unique as a dwarf planet not considered a TNO.