The correct answer is A. Bessemer pig.
Bessemer pig is a type of pig iron that is used in the Bessemer process to make steel. It is a high-quality pig iron that is free of impurities. It is made by melting iron ore in a blast furnace and then removing the impurities from the molten iron.
Grey pig is a type of pig iron that is not as pure as Bessemer pig. It contains more impurities, such as carbon and silicon. It is made by melting iron ore in a blast furnace and then not removing all of the impurities from the molten iron.
White forge pig is a type of pig iron that is even less pure than grey pig. It contains even more impurities, such as carbon and silicon. It is made by melting iron ore in a blast furnace and then not removing any of the impurities from the molten iron.
Mottled pig is a type of pig iron that is a mixture of grey pig and white forge pig. It contains some impurities, but it is not as pure as Bessemer pig. It is made by melting iron ore in a blast furnace and then removing some of the impurities from the molten iron.
The Bessemer process is a process for making steel from pig iron. It was invented by Henry Bessemer in 1856. The Bessemer process is a very efficient process for making steel. It is also a very fast process. The Bessemer process was the main process for making steel until the invention of the open-hearth process in the late 19th century.