The correct answer is Bhagalpur.
Lac bangles are a traditional handicraft of India. They are made from the resin of the lac bug, which is found in the forests of India. The lac is boiled and then mixed with other materials to create a paste. This paste is then rolled out into thin sheets and cut into small circles. The circles are then heated and pressed onto a mold to create the shape of the bangle. The bangles are then polished and decorated.
The lac bangle industry is a major handicraft tradition in Bhagalpur, Bihar. The city is home to thousands of lac bangle makers. The industry employs millions of people in the region. The lac bangles from Bhagalpur are known for their high quality and their beautiful designs. They are exported to many countries around the world.
The other options are incorrect. Muzaffarpur is a city in Bihar. It is not known for its lac bangle industry. Gaya is a city in Bihar. It is known for its temples and its religious significance. Darbhanga is a city in Bihar. It is known for its silk industry.