Give the decreasing order of `SN^2` reactivity of the following alkoxide nucleophile.
`Me_3 CO^(Ө), MeCH_2O^(Ө), Me_2CHO^(Ө)`

Explanation

To determine the decreasing order of SN2 reactivity of the given alkoxide nucleophiles: `Me3CO^(-)`, `MeCH2O^(-)`, and `Me2CHO^(-)`, we need to analyze the structures and steric hindrance of each alkoxide ion.

### Step-by-Step Solution:

1. **Identify the Structures**:
- **A**: `Me3CO^(-)` (tert-butoxide) - This alkoxide has three methyl groups attached to the central carbon.
- **B**: `MeCH2O^(-)` (methanol alkoxide) - This alkoxide has one methyl group and two hydrogen atoms attached to the central carbon.
- **C**: `Me2CHO^(-)` (isopropyl alkoxide) - This alkoxide has two methyl groups and one hydrogen atom attached to the central carbon.
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