Acids and ester having the same number of carbon atoms are:

Options

A. Functional isomers
B. Tautomers
C. Metamers
D. Not isomers

Explanation

To solve the question regarding acids and esters having the same number of carbon atoms, we need to understand the concepts of isomerism, particularly functional isomerism.

### Step-by-Step Solution:

1. **Identify the Functional Groups**:
- Acids have the functional group represented as -COOH (carboxylic acid).
- Esters have the functional group represented as -COOR (where R is an alkyl group).

2. **Understand the Definition of Isomers**:
- Isomers are compounds that have the same molecular formula but different structures or functional groups.

3. **Determine the Relationship Between Acids and Esters**:
- Both acids and esters can have the same number of carbon atoms in their molecular structure. For example, acetic acid (CH3COOH) and ethyl acetate (CH3COOCH2CH3) both contain two carbon atoms.

4. **Classify the Type of Isomerism**:
- Since acids and esters have different functional groups (-COOH for acids and -COOR for esters), they are classified as functional isomers. Functional isomers are compounds that have the same molecular formula but different functional groups.

5. **Conclusion**:
- Therefore, the correct answer to the question is that acids and esters having the same number of carbon atoms are functional isomers.

### Final Answer:
The correct answer is **functional isomers**.

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