Which Sultan of Slave dynasty reigned for the longest period?

The correct answer is Option 2 - Iltutmish

Iltutmish reigned for the longest period (1211-1236) among the Sultans of the Slave Dynasty. He was the second Sultan of the dynasty and is considered to be its greatest ruler. He consolidated the power of the Delhi Sultanate and expanded its territory. He also made important reforms to the administration and economy of the empire.

The other Sultans of the Slave Dynasty reigned for the following periods:

• Qutub ud din Aibak (1206-1210)
• Balban (1266-1287)
• Allauddin Khilji (1296-1316)