The correct answer is (a) Gautam Buddha Nagar.
Gautam Buddha Nagar is a district in the Indian state of Uttar Pradesh. It is the most populous district in the state, with a population of over 3.5 million. The district is located in the National Capital Region and is home to the city of Noida.
The literacy rate in Gautam Buddha Nagar is 89.5%, which is higher than the national average of 74.04%. The district has a number of educational institutions, including the Indian Institute of Technology, Delhi, the Indian Institute of Management, Lucknow, and the University of Delhi.
The other options are incorrect because they are not the most literate districts in Uttar Pradesh. Ghaziabad has a literacy rate of 84.1%, Kanpur Nagar has a literacy rate of 82.7%, and Lucknow has a literacy rate of 81.6%.
Gautam Buddha Nagar is the most literate district in Uttar Pradesh because it has a number of educational institutions, a high literacy rate, and a young population. The district is also home to a number of industries, which provides employment opportunities for the people.