The correct answer is: A. Vaishali
Vaishali was the capital of the Anga Mahajanpada, one of the 16 Mahajanapadas (great kingdoms) of ancient India. It was located in the present-day state of Bihar, India. Vaishali was an important center of trade and commerce, and was also a major Buddhist and Jain pilgrimage site.
The city was founded in the 6th century BCE by the Videha kings. It was ruled by a council of elected representatives, known as the gana-sangha. Vaishali was a major center of learning and culture, and was home to many famous scholars and philosophers.
The city was sacked by the Magadha king Ajatasatru in the 5th century BCE. However, it continued to be an important center of trade and commerce until the 6th century CE.
Vaishali is one of the oldest continuously inhabited cities in the world. It is a UNESCO World Heritage Site.
Option B, Rajgir, was the capital of the Magadha Mahajanpada. Option C, Patliputra, was the capital of the Mauryan Empire. Option D, Champa, was the capital of the Champa Kingdom.