The correct answer is Hindi.
Hindi is the official language of Bihar and is spoken by the majority of the population. English is also widely spoken, especially in urban areas. Bhojpuri is a regional language that is spoken by a significant minority of the population.
There are a number of newspapers published in Bihar, both in Hindi and English. The most popular Hindi newspapers include Dainik Jagran, Prabhat Khabar, and Hindustan Dainik. The most popular English newspapers include The Times of India, The Hindu, and The Indian Express.
A mix of Hindi and English is also used in some newspapers, particularly those that are aimed at a younger audience. This is known as Hinglish.