There are three isomeric compounds `P,Q,R` with molecular formula `C_(4)H_(6)O_(3)`.Compound `P` is a saturated hydroxy carboxylic acid.Compound `Q` is a symmetrical anhydride while `R` is an aldehydic ester.
Which of the following is the metamer of `Q`?

Options

A. `CH_(3)-oversetoverset(O)(||)(C)-O-oversetoverset(O)(||)(C)-CH_(3)`
B. `H-oversetoverset(O)(||)(C)-O-oversetoverset(O)(||)(C)-CH_(2)-CH_(3)`
C. `H-oversetoverset(O)(||)(C)-O-CH_(2)-oversetoverset(O)(||)(C)-CH_(3)`
D. `CH_(3)-O-oversetoverset(O)(||)(C)-oversetoverset(O)(||)(C)-OCH_(3)`

Answer

To determine the metamer of compound Q, we first need to understand the structures of the isomeric compounds P, Q, and R based on the given molecular formula C4H6O3.

### Step 1: Identify Compound P
- **Description**: Compound P is a saturated hydroxy carboxylic acid.
- **Structure**: Since it is saturated, it cannot have double or triple bonds. The hydroxy (-OH) group must be attached to a carbon atom in the carboxylic acid (-COOH) group.
- **Possible Structure**: One possible structure for P is 3-hydroxybutanoic acid (or 3-hydroxybutyric acid), which can be represented as:
\[ CH_3-CH(OH)-CH_2-COOH \]

### Step 2: Identify Compound Q
- **Description**: Compound Q is a symmetrical anhydride.
- **Structure**: A symmetrical anhydride can be formed from two identical carboxylic acids. The general structure of an anhydride is RCO-O-COR.
- **Possible Structure**: For Q, a possible symmetrical anhydride with the formula C4H6O3 is:
\[ (CH_3CO)_2O \]
This can be represented as:
\[ CH_3C(=O)O-C(=O)CH_3 \]

### Step 3: Identify Compound R
- **Description**: Compound R is an aldehydic ester.
- **Structure**: An aldehydic ester contains both an aldehyde (-CHO) and an ester (-COOR) functional group.
- **Possible Structure**: One possible structure for R could be:
\[ CH_3C(=O)OCH_2CHO \]
This structure contains a methyl ester and an aldehyde.

### Step 4: Identify the Metamer of Q
- **Definition of Metamer**: Metamers are isomers that differ in the arrangement of the carbon chains around a functional group, while having the same functional group.
- **Finding the Metamer**: For compound Q (the symmetrical anhydride), we can shift the position of the anhydride functional group to create a different structure while keeping the same molecular formula.
- **Possible Metamer Structure**: By rearranging the carbon chains, we can form:
\[ CH_3-CH_2-C(=O)-O-C(=O)-CH_3 \]
This is a different arrangement of the same functional groups, thus it is a metamer of Q.

### Conclusion
The metamer of compound Q is:
\[ CH_3-CH_2-C(=O)-O-C(=O)-CH_3 \]