Among the following four structures I to IV
I `{:(" "CH_(3)),(" "|),(C_(2)H_(5)-CH-C_(3)H_(7)):}`
II `{:(" "O" "CH_(3)),(" || |"),(CH_(3)-C-CH-C_(2)H_(5)):}`
III `H-undersetHunderset|oversetHoverset|(C^(oplus))`
IV `overset(CH_(3))overset(|)underset(C_(2)H_(5)-CH-C_(2)H_(5)` it is true that

Options

A. all four are chiral compounds
B. I and II are chiral compounds
C. III is a chiral compounds
D. II and IV are chiral compounds

Explanation

To determine which of the given structures (I to IV) are chiral compounds, we need to analyze each structure based on the definition of chirality. A chiral compound is one that has a carbon atom bonded to four different groups.

### Step-by-Step Solution:

1. **Analyze Structure I:**
- Structure I has a carbon atom that is attached to four different groups:
- CH3 (methyl group)
- C2H5 (ethyl group)
- C3H7 (propyl group)
- H (hydrogen)
- Since all four groups are different, Structure I is **chiral**.

2. **Analyze Structure II:**
- Structure II has a carbon atom bonded to:
- CH3 (methyl group)
- C2H5 (ethyl group)
- C=O (carbonyl group)
- H (hydrogen)
- All four groups attached to this carbon are different, making Structure II **chiral**.

3. **Analyze Structure III:**
- Structure III has a carbon atom bonded to:
- H (hydrogen)
- CH3 (methyl group)
- C2H5 (ethyl group)
- C2H5 (another ethyl group)
- Here, two of the groups (C2H5) are the same, which means this carbon does not have four different groups. Therefore, Structure III is **not chiral**.

4. **Analyze Structure IV:**
- Structure IV has a carbon atom bonded to:
- CH3 (methyl group)
- C2H5 (ethyl group)
- C2H5 (another ethyl group)
- H (hydrogen)
- Similar to Structure III, two of the groups (C2H5) are the same. Thus, Structure IV is also **not chiral**.

### Conclusion:
From the analysis:
- Structures I and II are chiral.
- Structures III and IV are not chiral.

Thus, the correct statement is that **only Structures I and II are chiral compounds**.