This quiz is really cumbersome since you only allow like one variant for each answer. I think you should make the word empire optional on all and allow things like Inca for Incan Empire. And also allow United Kingdom and UK for British Empire, and Moghul and Mogul for the Mughal Empire.
Well, first of all, it wasn't called the UK it was called the British Empire. Furthermore, Inca and Moghul weren't actual countries, it shouldn't be that cumbersome to type in Empire.