Select the odd one out with justification :
`NH_3, H_2 O , CaO , CH_4`

Explanation

To solve the problem of selecting the odd one out from the compounds NH₃ (ammonia), H₂O (water), CaO (calcium oxide), and CH₄ (methane), we will analyze the type of chemical bonding present in each compound.

### Step-by-Step Solution:

1. **Identify the Compounds and Their Bonds:**
- **NH₃ (Ammonia):**
- Type of bond: Covalent bonds.
- Structure: Pyramidal shape with one lone pair of electrons.
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