Stainless steel is corrosion resistant be cause of:

Options

A. alloying
B. painting
C. greasing
D. electroplating

Explanation

**Step-by-Step Solution:**

1. **Understanding Stainless Steel**:
- Stainless steel is an alloy primarily composed of iron and chromium.

2. **Composition of Stainless Steel**:
- The chromium content in stainless steel is typically around 10.5%. In addition to chromium, other elements such as nickel may also be present in smaller amounts.

3. **Corrosion of Iron**:
- Pure iron is prone to corrosion when exposed to air and moisture. This corrosion leads to degradation of its strength and appearance.

4. **Role of Chromium**:
- When chromium is added to iron to form stainless steel, it significantly alters the properties of the metal.

5. **Formation of Protective Layer**:
- Chromium reacts with oxygen in the air to form a thin, protective layer of chromium oxide on the surface of the stainless steel.

6. **Corrosion Resistance**:
- This chromium oxide layer acts as a barrier that prevents further oxidation of the underlying iron, thus making stainless steel corrosion resistant.

7. **Conclusion**:
- Therefore, stainless steel is corrosion resistant because of the presence of chromium, which forms a protective layer when exposed to air.