The compound X on reaction with `HgSO_4+H_2SO_4` gives
Y which one oxidation gives acetic acid. X is

Options

A. `C_2H_2`
B. `C_2H_4`
C. `C_3H_4`
D. `C_4H_6`

Explanation

To solve the problem, we need to identify the compound X that reacts with `HgSO4 + H2SO4` to form compound Y, which upon oxidation yields acetic acid.

### Step-by-Step Solution:

1. **Understanding the Reaction**:
The problem states that compound X reacts with `HgSO4 + H2SO4` to form compound Y. The reaction of an alkyne with sulfuric acid (in the presence of mercury sulfate) typically leads to the formation of an aldehyde.

2. **Identifying Compound Y**:
The compound Y is formed from the reaction of X and is further oxidized to yield acetic acid (CH3COOH). The only aldehyde that can be oxidized to acetic acid is acetaldehyde (CH3CHO).

3. **Determining Compound X**:
To produce acetaldehyde from an alkyne, we consider the simplest alkyne, which is ethyne (C2H2). When ethyne reacts with `HgSO4 + H2SO4`, it undergoes hydration to form acetaldehyde.

4. **Reaction Mechanism**:
- The ethyne (C2H2) reacts with sulfuric acid in the presence of mercury(II) sulfate to form vinyl alcohol (which is unstable and tautomerizes to acetaldehyde).
- The acetaldehyde can then be oxidized to acetic acid.

5. **Conclusion**:
Therefore, the compound X that reacts to form Y (acetaldehyde) which is oxidized to acetic acid is ethyne (C2H2).

### Final Answer:
The compound X is **C2H2 (ethyne)**.