Bihar was a center for trade union activities among workers in industries like:

The correct answer is: All of the above.

Bihar was a center for trade union activities among workers in industries like mining, railways, and textiles.

• Mining: The coal mines in Bihar were a major source of employment for workers, and the conditions in the mines were often dangerous and unhealthy. This led to a number of strikes and protests by miners, who demanded better working conditions and higher wages.
• Railways: The railways were another major employer in Bihar, and the workers on the railways were also subject to poor working conditions. This led to a number of strikes and protests by railway workers, who demanded better working conditions and higher wages.
• Textiles: The textile mills in Bihar were also a major source of employment for workers, and the conditions in the mills were often dangerous and unhealthy. This led to a number of strikes and protests by textile workers, who demanded better working conditions and higher wages.

The trade union movement in Bihar was a powerful force for change, and it played a major role in improving the lives of workers in the state.