Answer: Northern West
Notes: Northern West agro-climatic regions of Bihar has the highest number of districts. It has 13 districts. It includes West Champaran, East Champaran, Siwan, Saran, Sitamarhi, Sheohar, Muzaffarpur, Vaishali, Madhubani, Darbhanga, Samastipur, Gopalganj, Begusarai.
