$CH_3-CH_2-O-CH_2-CH_3$ and $CH_3-O-CH_2-CH_2-CH_3$ are

Which one of the following pairs of compounds are functional isomers?

Among the four compounds,$(i)$ acetone,$(ii)$ propanol,$(iii)$ methyl acetate and $(iv)$ propionic acid,the two that are isomeric are

The number of possible structural isomers for the molecular formula $C_3H_5Cl$ is ...............

For which of the following factors can the structural isomers $C_2H_5OH$ and $CH_3OCH_3$ be assumed to have the same value? (Assuming ideal behavior)

Which of the following pairs represents metamers?