The correct answer is Dhanbad.
Dhanbad is a district in the Indian state of Jharkhand. It is the second most populous district in Jharkhand after Ranchi. Dhanbad is known for its coal mines and is one of the major coal-producing districts in India. The district is also home to a number of mica mines.
Mica is a mineral that is used in a variety of applications, including electrical insulation, cosmetics, and roofing. The mica mines in Dhanbad are some of the largest in the world. The district is estimated to have reserves of over 100 million tonnes of mica.
The mica mines in Dhanbad are a major source of employment for the local population. However, the mining industry has also been blamed for environmental degradation and health problems in the district.
The other options are incorrect. Ranchi is the capital of Jharkhand and is not known for its mica mines. Bokaro is a district in Jharkhand that is known for its steel industry. Giridih is a district in Jharkhand that is known for its coal mines.