`H_2 S` is a

Options

A. strong dibasic acid
B. weak monobasic acid
C. weak dibasic acid
D. strong monobasic acid

Explanation

To determine what `H2S` (hydrogen sulfide) is, we can analyze its properties and behavior in water.

### Step-by-Step Solution:

1. **Understanding the Composition of H2S**:
- Hydrogen sulfide consists of two hydrogen atoms and one sulfur atom. Its chemical formula is `H2S`.

2. **Behavior in Water**:
- When `H2S` is dissolved in water, it can dissociate to release protons (H+ ions). This is a characteristic of acids.

3. **Acidic Nature**:
- `H2S` can donate protons (H+) to water, which means it behaves as an acid. Specifically, it can donate two protons because there are two hydrogen atoms in its structure.

4. **Classification of Acids**:
- Acids can be classified as monobasic or dibasic based on the number of protons they can donate:
- Monobasic acids can donate one proton.
- Dibasic acids can donate two protons.

5. **Strength of the Acid**:
- Although `H2S` can donate two protons, it does so weakly compared to strong acids. Therefore, it is classified as a weak acid.

6. **Conclusion**:
- Since `H2S` can donate two protons and is a weak acid, it is classified as a weak dibasic acid.

### Final Answer:
`H2S` is a **weak dibasic acid**.