Who amongst the following rulers of Delhi Sultanate built Alai Darwaza?

Q. Who amongst the following rulers of Delhi Sultanate built Alai Darwaza?
Answer: Allauddin Khilji
Notes: Allauddin Khilji patronised art and architecture in his reign as he built many forts viz. Alai Darwaza (the gateway to Qutub Minar), Siri fort, Hazar situr, Hauz-i-Allai, etc.