Which of the following metals cannot be extracted by the smelting process ?
`Al, Zn, Fe` and `Pb`.

Explanation

To determine which of the metals cannot be extracted by the smelting process among Aluminium (Al), Zinc (Zn), Iron (Fe), and Lead (Pb), we need to analyze the properties of these metals and their ores.

### Step-by-Step Solution:

1. **Understanding Smelting**:
- Smelting is a process that involves heating ores to extract metals. It typically uses carbon or carbon monoxide as a reducing agent to convert metal oxides into pure metals.

2. **Analyzing Each Metal**:
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