Auto-reduction process is used for the extraction of :

Options

A. Cu
B. Hg
C. Pb
D. Al

Explanation

To determine which metals are extracted using the auto-reduction process, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Auto-reduction Process**:
The auto-reduction process is a method used to extract certain metals from their sulfide ores. This process involves the reduction of metal sulfides to their respective metals.

2. **Identify the Metals in Question**:
The metals given in the question are Copper (Cu), Mercury (Hg), Lead (Pb), and Aluminium (Al).

3. **Research the Sulfides of Each Metal**:
- Copper sulfide (CuS)
- Mercury sulfide (HgS)
- Lead sulfide (PbS)
- Aluminium does not form a sulfide that is typically reduced in this manner.

4. **Determine Which Metals Are Extracted via Auto-reduction**:
The auto-reduction process is applicable to the sulfides of Copper, Mercury, and Lead. These metals are extracted from their sulfides during the auto-reduction process.

5. **Conclude the Answer**:
Since Aluminium (Al) is not extracted using the auto-reduction process, the metals that are extracted using this method are Copper (Cu), Mercury (Hg), and Lead (Pb). Therefore, the correct options are 1 (Cu), 2 (Hg), and 3 (Pb).

### Final Answer:
The auto-reduction process is used for the extraction of Copper (Cu), Mercury (Hg), and Lead (Pb).

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