Rank the following in decreasing order of basic strength is :
(A) `CH_3-CH_2-C-=C^(-)` (B) `CH_3-CH_2-S^(-)`
(C) `CH_3 - CH_2 -CO_(2)^(-)` (D) `CH_3-CH_2-O^(-)`

Options

A. `B gt A gt D gt C`
B. `D gt A gt B gt C`
C. `A gt D gt B gt C`
D. `A gt D gt C gt B`

Explanation

To rank the given compounds in decreasing order of basic strength, we need to analyze the stability of the anions formed from each compound. Basic strength is inversely related to the stability of the anion: the less stable the anion, the stronger the base.

### Step-by-Step Solution:

1. **Analyze Compound A: `CH3-CH2-C≡C^(-)`**
- The anion here is a carbon anion (alkyne anion). Carbon with a negative charge is highly unstable due to its electronegativity. Therefore, this anion is less stable and has a high tendency to donate electrons, making it a strong base.

2. **Analyze Compound B: `CH3-CH2-S^(-)`**
- The anion here is a thiolate ion. Sulfur is less electronegative than oxygen, which means that the negative charge on sulfur is less stable than that on oxygen. However, thiolates are still stronger bases than alcohols because they are less stable than the corresponding conjugate acids (thiols).

3. **Analyze Compound D: `CH3-CH2-O^(-)`**
- The anion here is an alkoxide ion. Oxygen is more electronegative than sulfur, which means that the negative charge on oxygen is more stable than that on sulfur. Therefore, the alkoxide ion is a weaker base compared to the thiolate ion.

4. **Analyze Compound C: `CH3-CH2-COO^(-)`**
- The anion here is a carboxylate ion. The negative charge is delocalized over two oxygen atoms, making it highly stabilized by resonance. This stabilization makes the carboxylate ion the weakest base among the given compounds.

### Summary of Basic Strength Ranking:
- **A (`CH3-CH2-C≡C^(-)`)**: Strongest base (least stable anion)
- **B (`CH3-CH2-S^(-)`)**: Second strongest base
- **D (`CH3-CH2-O^(-)`)**: Third strongest base
- **C (`CH3-CH2-COO^(-)`)**: Weakest base (most stable anion)

### Final Order:
1. A > B > D > C