The correct answer is B. Patna.
Patna is the capital of Bihar and the most populous city in the state. It is also the seat of the Patna High Court and the headquarters of the Patna division. The city has a long and rich history, dating back to the 6th century BC. It was the capital of the Magadha Empire, one of the largest and most powerful empires in ancient India. Patna is also home to a number of important educational institutions, including the Patna University, the Indian Institute of Technology Patna, and the National Institute of Technology Patna.
According to the Census of 2011, the literacy rate in Patna was 83.5%, which is higher than the national average of 74.04%. This is due to a number of factors, including the availability of educational facilities, the government’s focus on education, and the city’s relatively high economic development.
The other options are incorrect because they have lower literacy rates than Patna. Banka has a literacy rate of 69.3%, Rohtas has a literacy rate of 67.8%, and Kishanganj has a literacy rate of 66.2%.
In conclusion, the district with the highest literacy rate in Bihar is Patna. This is due to a number of factors, including the availability of educational facilities, the government’s focus on education, and the city’s relatively high economic development.