The correct answer is D. all of the above.
Annual operating expenditure of a power plant consists of fixed charges, semi-fixed charges, and running charges.
Fixed charges are those that do not vary with the output of the power plant. They include charges such as depreciation, interest on loans, and property taxes.
Semi-fixed charges are those that vary with the output of the power plant, but not in direct proportion to the output. They include charges such as fuel costs and maintenance costs.
Running charges are those that vary directly with the output of the power plant. They include charges such as labor costs and water costs.
The annual operating expenditure of a power plant is a significant cost that must be considered in the planning and operation of the plant. The cost of operating a power plant can be reduced by using efficient equipment, by operating the plant at its most efficient output level, and by negotiating favorable contracts with suppliers.