Taxila and its significance
Taxila, located in present-day Pakistan, was a prominent ancient city that served as a center of education and learning in the Indian subcontinent. It played a crucial role in the development and dissemination of knowledge during ancient times.

Mahajanapdas and their capitals
During the ancient period, the Indian subcontinent was divided into several Mahajanapdas, which were large territorial units ruled by powerful kings. Each Mahajanapda had its own capital city. Some of the well-known Mahajanapdas include Kashi, Vajji, Gandhar, and Patliputra.

The capital of Gandhar
The correct answer to the question is option 'B' - Gandhar. Taxila was the capital of the Mahajanapda Gandhar. Gandhar, also known as the Kingdom of Gandhara, was an ancient region located in present-day northern Pakistan and eastern Afghanistan.

Importance of Taxila as the capital of Gandhar
1. Educational hub: Taxila was renowned for its educational institutions and became a prominent center of learning in ancient times. It attracted scholars and students from various parts of the Indian subcontinent and beyond.
2. Buddhist center: Taxila played a significant role in the spread of Buddhism. It was a major Buddhist center where Buddhist teachings and philosophy flourished.
3. Cultural exchange: Taxila was a melting pot of various cultures and civilizations. It witnessed a rich exchange of ideas, knowledge, and cultural practices between different regions.
4. Trade and commerce: Located on important trade routes, Taxila thrived as a center of trade and commerce. The city's prosperity was fueled by the trade of goods, including textiles, spices, and precious stones.
5. Architectural heritage: Taxila boasts several archaeological sites and ruins that reflect the architectural brilliance of the ancient period. The remnants of Buddhist stupas, monasteries, and other structures are evidence of the city's grandeur.

In conclusion
Taxila, the center of education, served as the capital of the Mahajanapda Gandhar. Its significance lies in its role as an educational hub, a Buddhist center, a site of cultural exchange, a thriving trade and commerce center, and its architectural heritage. The city played a crucial role in the development and dissemination of knowledge during ancient times.