The correct answer is D. Gaya.
BIADA is a state government undertaking of Bihar. It was established in 1974 with the objective of promoting and developing industries in the state. BIADA has its headquarters at Patna and has regional offices at Darbhanga, Bhagalpur, Muzaffarpur, and Purnia.
Gaya is a city in the state of Bihar. It is the headquarters of Gaya district and the divisional commissionerate of Magadh division. Gaya is one of the oldest cities in India and is a major pilgrimage destination for Hindus. The city is also home to a number of educational institutions and industries.
However, Gaya does not have a regional office of BIADA. The nearest BIADA regional office is located at Patna.