The correct answer is B. Tungsten.
Stainless steel is an alloy of iron with a minimum of 10.5% chromium. The chromium forms a chromium oxide layer on the surface of the steel, which protects it from corrosion. Other elements that may be added to stainless steel include nickel, molybdenum, and manganese.
Tungsten is a metal that is not typically used in stainless steel. It is a very hard metal that is resistant to wear and tear. However, it is also very expensive and difficult to work with. As a result, it is not often used in stainless steel.
The other options, iron, chromium, and nickel, are all common elements in stainless steel. Iron is the main component of stainless steel, and chromium is what gives stainless steel its corrosion resistance. Nickel is often added to stainless steel to improve its toughness and machinability.