The correct answer is A. Kishanganj.
Kishanganj is a district in the Indian state of Bihar. It is the largest producer of tea in Bihar. The tea industry in Kishanganj is a major source of employment for the local people. The tea gardens in Kishanganj are spread over an area of about 10,000 hectares. The main varieties of tea grown in Kishanganj are Assam, Darjeeling, and Nilgiri. The tea industry in Kishanganj is facing a number of challenges, including low productivity, lack of infrastructure, and poor marketing. However, the government is taking steps to address these challenges and promote the tea industry in Kishanganj.
The other options are incorrect because:
- B. Purnea is not the largest producer of tea in Bihar. The tea industry in Purnea is not as developed as the tea industry in Kishanganj.
- C. Darbhanga is not the largest producer of tea in Bihar. The tea industry in Darbhanga is not as developed as the tea industry in Kishanganj.
- D. Araria is not the largest producer of tea in Bihar. The tea industry in Araria is not as developed as the tea industry in Kishanganj.