Of the following the most acidic is.

Options

A. `H_3 PO_4`
B. `H_3 AsO_4`
C. `H_3 SbO_4`
D. `H_3 BiO_4`

Explanation

To determine which of the given oxyacids is the most acidic, we will analyze the acids provided: H3PO4 (phosphoric acid), H3SO4 (sulfuric acid), H3SbO4 (antimonic acid), and H3BiO4 (bismuthic acid).

### Step-by-Step Solution:

1. **Identify the Acids**: We have four oxyacids:
- H3PO4 (phosphoric acid)
- H3SO4 (sulfuric acid)
- H3SbO4 (antimonic acid)
- H3BiO4 (bismuthic acid)

2. **Understand the Trend in Acidity**: Acidity of oxyacids generally increases with the electronegativity of the central atom and the number of oxygen atoms bonded to it. As we move down the group in the periodic table, the metallic character increases, and the acidity tends to decrease.

3. **Order of Acidity**: The order of acidity for the oxyacids of group 15 elements is generally:
- H3PO4 (most acidic)
- H3AsO4
- H3SbO4
- H3BiO4 (least acidic)

4. **Comparison of Acids**:
- H3SO4 is not part of group 15 but is known to be a strong acid.
- Comparing H3PO4 and H3SO4, H3SO4 is stronger than H3PO4.
- H3SbO4 and H3BiO4 are weaker than H3PO4.

5. **Conclusion**: Among the given acids, H3SO4 is the most acidic, followed by H3PO4. Therefore, the most acidic acid from the options provided is H3SO4.

### Final Answer:
The most acidic among the given options is **H3SO4 (sulfuric acid)**.