Select the odd out and justify your choice
`CaO, CuO, BaO, MgO`

Explanation

To solve the problem of selecting the odd one out from the given oxides: CaO, CuO, BaO, and MgO, we can follow these steps:

### Step 1: Identify the elements in the oxides
- **CaO** (Calcium oxide): Calcium (Ca) is an alkaline earth metal.
- **CuO** (Copper oxide): Copper (Cu) is a transition metal.
- **BaO** (Barium oxide): Barium (Ba) is an alkaline earth metal.
- **MgO** (Magnesium oxide): Magnesium (Mg) is an alkaline earth metal.

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