Select odd one out which does not fit as required and justify your answer
Na, Cu, Mg, Hg `" "`Solid state

Explanation

To solve the question of selecting the odd one out among Na (Sodium), Cu (Copper), Mg (Magnesium), and Hg (Mercury) based on their state at room temperature, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Elements**: We have four elements: Sodium (Na), Copper (Cu), Magnesium (Mg), and Mercury (Hg).

2. **Determine the State of Each Element**:
- Sodium (Na): Solid at room temperature.
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