Ur asked which one is Maximum expenditure plant. Expenditure in power plants are consider in following terms Initial cost,maintenance cost,disposal cost.
In Hyde power plant initial cost is high, and maintenance & disposal cost is low.
In nuclear power plant is initial & disposal cost is high. maintenance cost is low compare to thermal power plant.
But thermal power plant initial, maintenance & disposal cost is high.
gas power plant initial & disposal cost is low. So the answer is C = thermal power plant