Which one of the following Departments is not under the Ministry of Home Affairs?

The Department of Drinking Water and Sanitation is not under the Ministry of Home Affairs; it is under the Ministry of Jal Shakti. The other three departments — Department of States, Department of Official Language, and Department of Border Management — are all under the Ministry of Home Affairs, along with other departments like Department of Internal Security, Department of Home, Department of Jammu & Kashmir Affairs, etc.