Arrange the following in order of increasing stability :
`CH_3 CH_2^(-) , CH -= C^(-) , CH_2 = CH^(-)`

Explanation

To arrange the given anions in order of increasing stability, we need to analyze the hybridization and s-character of the carbon atoms involved in each anion. The stability of anions is influenced by the ability of the carbon atom to stabilize the negative charge, which is determined by the hybridization state and the corresponding s-character.

### Step-by-Step Solution:

1. **Identify the Anions:**
- The given anions are:
- \( CH_3CH_2^- \) (ethyl anion)
- \( CH \equiv C^- \) (acetylide anion)
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