Arrange the following carbon atoms numbered `C-1, C-2 and C-3` in the decreasing order of s - character :
`H_(3)-C-overset(1)CH_(2)-overset(O)overset(||)(C^(2))-CH_(2)-overset(3)C-=C-CH_(3)`

Explanation

To determine the decreasing order of s-character for the carbon atoms numbered C-1, C-2, and C-3 in the given hydrocarbon structure, we need to analyze the hybridization of each carbon atom.

### Step-by-Step Solution:

1. **Identify the Structure**:
The given structure is:
```
H3C-CH2-C(=O)-CH2-C≡C-CH3
...