Explanation: The Slave Dynasty, also known as the Mamluk Dynasty, was the first dynasty of the Delhi Sultanate in India. It was established by Qutb-ud-din Aibak, who was a slave of Muhammad Ghori and became the first sultan of Delhi after Ghori's death. The dynasty was characterized by the rule of several sultans who were originally slaves, hence the name "Slave Dynasty."
The dynasty saw several notable rulers, including Iltutmish, who expanded the empire significantly, and Razia Sultana, the first female ruler of the Delhi Sultanate. However, the dynasty's power began to wane towards the end of the 13th century. Ghiasuddin Balban, who ruled from 1266 to 1287, was one of the most powerful rulers of the dynasty. He was known for his strong administrative reforms and military campaigns that helped stabilize the empire.
After Balban's death, his grandson, Qaiqabad, ascended the throne in 1287. Qaiqabad was a weak ruler and was heavily influenced by his mother, Malika-i-Jahan. The empire faced internal strife and external threats during his reign. In 1290, Qaiqabad was succeeded by his prime minister, Jalal-ud-din Firuz Khilji, who was later overthrown by his nephew, Alauddin Khalji, in 1296. Alauddin Khalji then established the Khalji dynasty, marking the end of the Slave Dynasty.
Thus, while Qaiqabad was the last legitimate ruler of the Slave Dynasty, the dynasty's effective rule ended with his reign. The correct answer is (D) Balban's grandson, as he was the last ruler of the Slave Dynasty before the transition to the Khalji dynasty.