Correct option is A
In a simple vapor power cycle of a steam power plant, the boiler plays a critical role in converting thermal energy into mechanical energy. Its main function is to heat water and convert it into high-pressure, high-temperature steam. This steam then expands in the turbine, producing mechanical work that can be converted into electricity. The boiler does not condense the steam (that is the role of the condenser), nor does it directly generate electricity or cool the working fluid. Its primary purpose is to supply the energy in the form of high-pressure steam required to drive the turbine efficiently.
