The correct answer is: The Vajjis.
The Vajjis were a powerful republican state in the Ganges Valley during the time of the Buddha. They were a confederation of 16 tribes, each with its own government. The Vajjis were known for their military prowess and their democratic system of government.
The Panchalas were another powerful republican state in the Ganges Valley. They were a confederation of 10 tribes, each with its own government. The Panchalas were known for their wealth and their cultural achievements.
The Kashis were a kingdom in the Ganges Valley. They were ruled by a king and had a hereditary system of government. The Kashis were known for their religious and commercial importance.
The Magadhas were a kingdom in the Ganges Valley. They were ruled by a king and had a hereditary system of government. The Magadhas were the most powerful kingdom in the Ganges Valley at the time of the Buddha. They eventually conquered the Vajjis and the Panchalas, and became the dominant power in the region.
The Vajjis were the most important republican state during the period of Buddha because they were the most powerful and influential of the republican states. They were also the most democratic of the republican states, and their system of government was admired by many.