Which one of the following pairs of isomers is an example of metamerism?

Metamerism in organic chemistry is a type of functional isomerism where compounds with the same molecular formula and functional group exhibit different alkyl group arrangements on either side of the functional group. These isomers, known as metamers, occur due to unequal distribution of carbon atoms around heteroatoms like Oxygen ($$O$$), Nitrogen ($$N$$), or Sulphur ($$S$$).

Metamers have the same functional group (e.g., ether, amine, ketone, ester) but differ in the carbon chain length attached to it. 

Thus option D has a pair of metamers (ketone functional group attached to different chain lengths).