The only metal which is liquid at `0^(@)C` is

Options

A. Iron
B. mercury
C. sodium
D. aluminium

Explanation

To solve the question, "The only metal which is liquid at `0^(@)C` is," we can follow these steps:

### Step 1: Identify the Metals
First, we need to identify the metals listed in the options:
- Option A: Iron (Fe)
- Option B: Mercury (Hg)
- Option C: Sodium (Na)
- Option D: Aluminium (Al)

### Step 2: Determine the Physical State of Each Metal at `0^(@)C`
Next, we need to determine the physical state (solid, liquid, or gas) of each metal at `0^(@)C`:
- Iron (Fe): Solid at `0^(@)C`
- Mercury (Hg): Liquid at `0^(@)C`
- Sodium (Na): Solid at `0^(@)C`
- Aluminium (Al): Solid at `0^(@)C`

### Step 3: Analyze the Properties of Mercury
Now, let's focus on Mercury:
- Mercury has a low melting point of approximately `-38.83^(@)C`, which means it is in a liquid state at `0^(@)C`.
- The weak metallic bonding in Mercury contributes to its ability to remain liquid at room temperature.

### Step 4: Conclusion
Based on the analysis, the only metal that is liquid at `0^(@)C` is Mercury (Hg).

### Final Answer
Therefore, the correct answer is **Option B: Mercury**.

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