and  are : A Functional isomer B Metamer C Position isomer D Chain isomer

The given options are A, B, C, and D.

To determine the correct answer, we need to understand the definitions of functional isomer, metamer, position isomer, and chain isomer.

1. Functional isomer: Functional isomers have the same molecular formula but differ in the functional group or the way the atoms are connected. They have different chemical properties due to the different functional groups.

2. Metamer: Metamers are a type of functional isomer where the molecular formula and functional group are the same, but the carbon skeleton is different. They have different alkyl groups attached to the functional group.

3. Position isomer: Position isomers have the same molecular formula and functional group, but the position of the functional group differs in the carbon chain.

4. Chain isomer: Chain isomers have the same molecular formula and functional group, but the carbon chain arrangement differs.

Now, let's analyze the given options:

A. Functional isomer: This option matches the definition of functional isomer, where the isomers differ in the functional group or the way the atoms are connected.

B. Metamer: This option matches the definition of metamer, where the isomers have the same molecular formula and functional group, but the carbon skeleton is different.

C. Position isomer: This option matches the definition of position isomer, where the isomers have the same molecular formula and functional group, but the position of the functional group differs in the carbon chain.

D. Chain isomer: This option matches the definition of chain isomer, where the isomers have the same molecular formula and functional group, but the carbon chain arrangement differs.

Based on the definitions and the given options, we can conclude that:

A is the correct answer for functional isomer. B is the correct answer for metamer. C is the correct answer for position isomer. D is the correct answer for chain isomer.