The correct option is A Vaishali
The seat of the first Rebuplic of the world in 6th century BC was in Vaishali. Vaishali was established in 6th century BCE as a republic, i.e., before the birth of Gautam Buddha, thereby making it the world's first republic. Vaishali was an ancient metropolis and the capital city of the republic of the Vajji confederation of Mithila, which covered most of the Himalayan Gangetic region of present-day Bihar.