Most acidic species among the following is

Options

A.
B.
C.
D.

Answer

To determine the most acidic species among the given options, we need to analyze the stability of the conjugate base (X-) formed when the acidic species (HX) donates a proton (H+). The more stable the conjugate base, the stronger the acid.

### Step-by-Step Solution:

1. **Identify the Acidic Species**:
We have several species (let's denote them as A, B, C, and D). We need to evaluate each one to determine which can donate a proton (H+) and form the most stable conjugate base.

2. **Understand Acidic Properties**:
The acidic property of a compound is determined by its ability to release H+. This release is favorable if the resulting conjugate base (X-) is stable.

3. **Evaluate Each Option**:
- **Option A**: This species has multiple hydrogen atoms that can be removed. However, when we analyze the stability of the resulting conjugate base, we find that the presence of electronegative oxygen atoms destabilizes the negative charge due to their electron-donating (+M) effect. Thus, the conjugate base formed from option A is not stable.

- **Option B**: Similar to option A, but with sulfur instead of oxygen. Sulfur is less electronegative than oxygen, which means it has a weaker +M effect. Therefore, the conjugate base formed from option B is more stable than that from option A, but still not the most stable.

- **Option C**: This option has a carbon atom that separates the acidic hydrogen from the electronegative oxygen atoms. When the hydrogen is removed, the resulting negative charge is not stabilized by resonance with the oxygen atoms. Instead, the electronegative oxygens exert a -I effect, pulling electron density away from the negative charge, which stabilizes it. Thus, the conjugate base from option C is more stable than those from options A and B.

- **Option D**: This species lacks any electronegative groups that could stabilize or destabilize the negative charge. Therefore, it is less stable than option C but more stable than A and B.

4. **Determine the Most Acidic Species**:
After comparing the stability of the conjugate bases formed from each option, we conclude that option C produces the most stable conjugate base. Therefore, it is the most acidic species among the given options.

### Final Answer:
**Option C is the most acidic species.**