An organic compound has molecular formula `C_(9)H_(18)`. It is a saturated hydrocarbon and its all hydrogen atoms are identical. Its structural formula can be `:`

Options

A.
B.
C.
D.

Explanation

To solve the problem, we need to determine the structural formula of the organic compound with the molecular formula C9H18, which is a saturated hydrocarbon with identical hydrogen atoms.

### Step-by-Step Solution:

1. **Identify the Type of Hydrocarbon**:
- The molecular formula C9H18 indicates that the compound is a saturated hydrocarbon (alkane). Saturated hydrocarbons have the general formula CnH2n+2. For n=9, the formula would be C9H20. However, since we have C9H18, it suggests that there are two fewer hydrogen atoms, indicating the presence of a ring or multiple substituents.

**Hint**: Remember that saturated hydrocarbons follow the formula CnH2n+2.

2. **Determine the Structure**:
- Since the compound is saturated and all hydrogen atoms are identical, it suggests that the structure is likely a cycloalkane. The simplest cyclic structure for a 9-carbon compound is cyclononane (C9H18).

**Hint**: Consider cycloalkanes when the number of hydrogen atoms is less than expected for a straight-chain alkane.

3. **Draw the Structural Formula**:
- The structural formula for cyclononane can be represented as a ring of nine carbon atoms, with each carbon atom bonded to two hydrogen atoms, except for the carbon atoms at the junctions which will have two hydrogen atoms each.

**Hint**: Visualize the structure as a closed loop of carbon atoms.

4. **Confirm the Identical Hydrogen Atoms**:
- In cyclononane, all hydrogen atoms are indeed identical because they are all attached to carbon atoms in the same environment. This satisfies the condition of the problem that all hydrogen atoms are identical.

**Hint**: Check if all hydrogen atoms are in the same chemical environment to ensure they are identical.

5. **Final Structural Representation**:
- The final structural formula of the compound can be drawn as a cyclic structure with nine carbon atoms, which can be represented as:
```
C
/ \
C C
/ \
C C
\ /
C---C
/ \
C C
\ /
C---C
```

**Hint**: Use a cyclic representation to depict the structure clearly.

### Conclusion:
The structural formula of the organic compound with the molecular formula C9H18, which is a saturated hydrocarbon with identical hydrogen atoms, is cyclononane.