The correct option is C Heat energy is converted into mechanical energy.
Steam engine is a machine used for converting heat energy into mechanical energy, using steam as the conversion medium. When water is boiled into steam its volume increases about 1,600 times, producing a force that can be used to move a piston back and forth in a cylinder. The piston is attached to a crankshaft that converts the piston's back-and-forth motion into rotary motion for driving machinery.