A hydrocarbon with formula `C_(8)H_(18)` gives one monochloro derivative. The hydrocarbon can be:

Options

A. `n`-octane
B. `2` Methyl heptane
C. `2,2,4`-Trimethyl pentane
D. `2,2,3,3`-Tetramethyl butane

Explanation

To determine which hydrocarbon with the formula \( C_8H_{18} \) gives only one monochloro derivative, we need to analyze the given options based on their structural characteristics and the degree of symmetry.

### Step-by-Step Solution:

1. **Understand the Hydrocarbon Formula**:
The formula \( C_8H_{18} \) indicates that we are dealing with an alkane (since it follows the general formula for alkanes \( C_nH_{2n+2} \)).

2. **List the Given Options**:
- Option 1: n-Octane
- Option 2: 2-Methylheptane
- Option 3: 2,2,4-Trimethylpentane
- Option 4: 2,2,3,3-Tetramethylbutane

3. **Analyze Each Option for Symmetry**:
- **n-Octane**: This is a straight-chain hydrocarbon (CH3-CH2-CH2-CH2-CH2-CH2-CH2-CH3). Chlorination can occur at multiple positions, leading to multiple monochloro derivatives. Thus, it does not fit our requirement.

- **2-Methylheptane**: This has a branched structure but still has multiple positions where chlorination can occur (at the heptane chain and the methyl group). Therefore, it can also produce more than one monochloro derivative.

- **2,2,4-Trimethylpentane**: This compound has a more complex branching structure. Chlorination can occur at several positions (the two methyl groups at position 2 and the methyl group at position 4), leading to multiple monochloro derivatives.

- **2,2,3,3-Tetramethylbutane**: This compound has a highly symmetrical structure. The chlorination can only occur at one specific position, leading to only one possible monochloro derivative.

4. **Conclusion**:
After analyzing all options, we find that **2,2,3,3-tetramethylbutane** is the only hydrocarbon that gives one monochloro derivative due to its symmetrical structure.

### Final Answer:
The hydrocarbon that gives one monochloro derivative is **2,2,3,3-tetramethylbutane** (Option 4).