Which element on treatment with caustic soda solution produces `H_(2)` gas?

Explanation

To determine which element reacts with caustic soda (NaOH) to produce hydrogen gas (H₂), we can analyze the reactions of certain metals with NaOH.

### Step-by-Step Solution:

1. **Identify the Reactant**:
- The reactant in question is caustic soda, which is chemically represented as sodium hydroxide (NaOH).

2. **Consider Possible Metals**:
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