The Tughlaqabad fort was built by Ghiyas-ud-din Tughlaq in 1321. The Bara Gumbad was constructed in 1490 during the reign of Sikandar Lodi. Qutub Minar is a soaring, 73 m-high tower of victory, built in 1193 by Qutub-ud-din Aibak. Fatehpur Sikri was founded as the capital of the Mughal Empire in 1571 by Emperor Akbar. So, option (b) is the correct code.