The correct answer is: A. Katihar
Katihar is a district in the Indian state of Bihar. It is located in the north-eastern part of the state and is bounded by the districts of Purnia to the north, Araria to the east, Bhagalpur to the south, and Jharkhand to the west. The district has a population of over 4.5 million people and is the third most populous district in Bihar.
The district is known for its four crops region, which is a fertile area that produces rice, wheat, maize, and sugarcane. The four crops region is located in the south-eastern part of the district and is home to a number of important towns and villages, including Katihar, Barsoi, and Sonbarsa.
The four crops region is a major agricultural area and is known for its high yields of rice, wheat, maize, and sugarcane. The region is also home to a number of important industries, including sugar mills, rice mills, and flour mills.
The four crops region is a major tourist destination and is home to a number of important historical and religious sites, including the Katihar Fort, the Barsoi Palace, and the Sonbarsa Temple.
The other options are incorrect because they are not districts in Bihar.