The fifth storey of the Qutub Minar was built during the reign of:

The Qutub Minar, in the Mehrauli area of Delhi, is one of the finest examples of early Indo-Islamic architecture. It is about 72.5 metres tall and is the tallest brick minaret in the world. It was declared a UNESCO World Heritage Site in 1993, together with the monuments around it.

The minar was built in stages by different rulers:

• Qutbuddin Aibak, the founder of the Delhi Sultanate, began its construction around 1199 and completed the first storey.
• Iltutmish, his successor and son-in-law, added three more storeys.

In 1368, the top storey was damaged by lightning. Firoz Shah Tughlaq repaired it, replacing the damaged top with two storeys, the fourth and the fifth, built with white marble along with red sandstone.

Later, Sikandar Lodi also carried out repairs in 1505, and in the 19th century the British added a cupola, which was later removed and now stands in the lawns as "Smith's Folly".

The minar is believed to be named after Qutbuddin Aibak or after the Sufi saint Khwaja Qutbuddin Bakhtiyar Kaki. It may have been built as a victory tower and also as a minaret for the call to prayer from the nearby Quwwat-ul-Islam mosque, the first mosque built in Delhi after the Turkish conquest.

The Qutub complex also includes the Iron Pillar, a Gupta-period pillar that has not rusted for about 1,600 years; the Alai Darwaza, built by Alauddin Khalji in 1311, with the first true arches and domes in India; the unfinished Alai Minar; and the tomb of Iltutmish.

Why not the other options?

• ✗Qutbuddin Aibak built only the first storey.
• ✗Iltutmish added the second, third and fourth storeys originally.
• ✗Alauddin Khalji built the Alai Darwaza and began the Alai Minar.