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 pairs are position isomers ?

Options

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

Explanation

To determine which pairs of the given compounds are position isomers, we need to analyze the structures based on their molecular formulas and the position of their functional groups.

### Step-by-Step Solution:

1. **Identify the Functional Groups:**
- For each compound, identify the functional groups present:
- I: Aldehyde (CHO)
- II: Ketone (C=O)
- III: Ketone (C=O)
- IV: Aldehyde (CHO)

2. **Check the Molecular Formula:**
- Calculate the molecular formula for each compound:
- I: C5H10O
- II: C5H10O
- III: C5H10O
- IV: C5H10O
- All compounds have the same molecular formula (C5H10O).

3. **Determine the Position of Functional Groups:**
- For position isomers, the functional groups must be the same but located at different positions on the carbon chain.
- Analyze the position of the functional groups:
- I: Aldehyde at the end of a straight chain (1st carbon).
- II: Ketone at the 2nd carbon.
- III: Ketone at the 3rd carbon.
- IV: Aldehyde at the end of a branched chain (1st carbon).

4. **Identify Pairs of Position Isomers:**
- Compare the functional groups and their positions:
- Compounds I and IV both have aldehyde groups, but they are not position isomers because their carbon chains are arranged differently.
- Compounds II and III both have ketone groups, but they are position isomers because the ketone is located at different positions (2nd and 3rd carbon) on the same carbon chain.

5. **Conclusion:**
- The only pair that qualifies as position isomers is **II and III**.

### Final Answer:
The pairs that are position isomers are **II and III**.