Detailed Solution:
The correct answer is “Badaun has the lowest sex ratio”.
1) As of the 2011 census, Prayagraj is the most populous district of Uttar Pradesh while Mahoba being the least populated.
2) According to Census 2011, Ghaziabad records the highest literacy rate in the state; Shravasti, on the other hand, records the lowest literacy rate in UP.
3) According to Census 2011 the district with the lowest sex ratio in Uttar Pradesh is Gautam Buddh Nagar.
4) Lakhimpur Kheri is the largest district in Uttar Pradesh, India, on the border with Nepal.