ANS:C - separate steam from water.

In a boiler drum, the process of separating steam from water occurs naturally due to the difference in density between steam and water. As water is heated and converted into steam, steam rises to the top of the drum because it is less dense than water. Meanwhile, any remaining water or liquid droplets fall to the bottom of the drum due to their higher density. This separation process ensures that only pure steam is drawn off from the top of the drum for further use, while any remaining water is retained in the drum. The separated steam is then directed to the steam distribution system for various applications, such as powering turbines or heating processes.