Common alloying elements in stainless steel Steps:

• Define stainless steel as an iron-carbon alloy with additional elements for corrosion resistance.
• Note that carbon provides basic steel properties, present in all steels at 0.03-2%.
• Identify nickel as a common addition in austenitic stainless steels (e.g., 304 grade) for improved formability and toughness.
• Eliminate options lacking standard elements by checking typical compositions (Fe >70%, C <0.1%, Ni 8-10%).

Why C is correct:

• Nickel enhances corrosion resistance and structure in many stainless steels, while carbon is essential per steel's definition as an Fe-C alloy (ASTM standards).

Why the others are wrong:

• A: Copper is rarely used; chromium is common but not paired with copper typically.
• B: Copper is not a standard alloying element in stainless steel.
• D: Zinc is used for galvanizing iron, not in stainless steel alloys.

Final answer: C