Right option is (d) Babcock-Wilcox boiler
The explanation is: If the boilers are used at one place only they are termed as stationary boilers. These boilers are used for either process heating in industries or for power generation in steam power plants. These are used at central station utility power plants, for plant process etc. Ex: Babcock-Wilcox boiler, Fluidized Bed Combustion (FBC) boiler.