I. `CH_(3)-CH_(2)-CH_(2)-CH_(2)-overset(O)overset(||)(C)-H`
II. `CH_(3)-CH_(2)-CH_(2)-overset(O)overset(||)(C)-CH_(3)`
III. `CH_(3)-CH_(2)-underset(O)underset(||)(C)-CH_(2)-CH_(3)`
IV. `{:(CH_(3)-CH-CH_(2)-C-H),(" |"" ||"),(" "CH_(3)" "O):}`
Which of the following are not functional group isomers ?

Options

A. II and III
B. II and IV
C. I and IV
D. I and II

Explanation

To determine which of the given compounds are not functional group isomers, we need to analyze their structures and identify their functional groups. Functional group isomers are compounds that have the same molecular formula but different functional groups.

### Step-by-Step Solution:

1. **Identify Molecular Formula of Each Compound**:
- For all compounds, count the number of carbon (C), hydrogen (H), and oxygen (O) atoms.
- All compounds have 5 carbon atoms, 10 hydrogen atoms, and 1 oxygen atom, leading to the molecular formula C5H10O.

2. **Identify Functional Groups**:
- **Compound I**: `CH3-CH2-CH2-CH2-CHO` (Aldehyde, -CHO)
- **Compound II**: `CH3-CH2-CH2-C(=O)-CH3` (Ketone, -C(=O)-)
- **Compound III**: `CH3-CH2-C(=O)-CH2-CH3` (Ketone, -C(=O)-)
- **Compound IV**: `CH3-CH-CH2-C(=O)-H` (Aldehyde, -CHO)

3. **Compare Functional Groups**:
- **Compound I**: Aldehyde
- **Compound II**: Ketone
- **Compound III**: Ketone
- **Compound IV**: Aldehyde

4. **Identify Non-Functional Group Isomers**:
- Compare the functional groups:
- Compounds II and III are both ketones, so they are not functional group isomers.
- Compounds I and IV are both aldehydes, so they are also not functional group isomers.
- Compound II (ketone) and Compound IV (aldehyde) are functional group isomers.

5. **Conclusion**:
- The pairs that are not functional group isomers are:
- **Option A**: Compound II and III (both are ketones)
- **Option C**: Compound I and IV (both are aldehydes)

### Final Answer:
The pairs that are not functional group isomers are:
- Compound II and III
- Compound I and IV