Select the strongest acid :

Options

A. `CF_(3)`COOH
B. `"CCl"_(3)`COOH
C. `CH_(3)`COOH
D. `CBr_(3)`COOH

Explanation

To determine the strongest acid among the given options (A, B, C, and D), we need to analyze the stability of the conjugate bases formed after the acid donates a proton (H⁺). The more stable the conjugate base, the stronger the acid.

### Step-by-Step Solution:

1. **Identify the Acids and Their Conjugate Bases**:
- **Option A**: CF3COOH → CF3COO⁻ (conjugate base)
- **Option B**: CCl3COOH → CCl3COO⁻ (conjugate base)
- **Option C**: CH3COOH → CH3COO⁻ (conjugate base)
- **Option D**: CBr3COOH → CBr3COO⁻ (conjugate base)

2. **Analyze the Conjugate Bases**:
- All conjugate bases (CF3COO⁻, CCl3COO⁻, CH3COO⁻, CBr3COO⁻) have a common structure where the negative charge is on the oxygen atom, which is stabilized by resonance with the carbonyl group (C=O).

3. **Consider the Electron-Withdrawing Effects**:
- The presence of electron-withdrawing groups (EWGs) like CF3, CCl3, and CBr3 increases the stability of the conjugate base by delocalizing the negative charge.
- **Fluorine (F)** is the most electronegative element, followed by **Chlorine (Cl)**, **Bromine (Br)**, and then **Hydrogen (H)**, which does not have an electron-withdrawing effect.

4. **Rank the Options Based on EWG Strength**:
- **Option A (CF3)**: Strongest EWG due to fluorine.
- **Option B (CCl3)**: Moderate EWG due to chlorine.
- **Option D (CBr3)**: Weaker EWG due to bromine.
- **Option C (CH3)**: No EWG effect.

5. **Conclusion**:
- Since CF3 is the strongest electron-withdrawing group, the conjugate base CF3COO⁻ will be the most stable, making CF3COOH the strongest acid among the options.

### Final Answer:
**The strongest acid is Option A: CF3COOH.**