Where was Anushilan Samiti Branch established in Bihar?

The correct answer is: B. Patna.

Anushilan Samiti was a revolutionary organisation founded in 1886 by Aurobindo Ghosh and Barindra Kumar Ghosh in Kolkata. It had branches in many parts of India, including Bihar. The Patna branch of Anushilan Samiti was established in 1906. It was one of the most active branches of the organisation and played a significant role in the Indian independence movement.

The other options are incorrect. Gaya is a city in Bihar. Muzaffarpur is a city in Bihar. Munger is a city in Bihar.