Nice quiz, but please add more accepted type-ins to make this a fair game. The word "Caliphate" should be optional, as is "Great" for the Seljuks. Also, Timur's Empire or Tamerlane's Empire or just Timur should be enough for that answer. In addition, I believe the Umayyad Caliphate was the largest Islamic Empire, not the Abbasid.
When I made this quiz, I searched multiple websites trying to figure out which is bigger. Most of them say they tie around 11.1 million square kilometers. Also, I think that it would be more like historical if we just type the full name of the empire. Respectfully, I do agree with your choice but after careful consideration I decided not to fix this quiz. Hope you understand. Have a good day!