The correct options are
A diethylether
B diethylketone
C diethylamine
The metamerism arises when different alkyl groups are attached to the same functional group and the molecular formula is same.
i) C2H5OC2H5 and CH3OC3H7 are metamers.
ii) C2H5COC2H5 and CH3COC3H7 metamers.
iii) C2H5NHC2H5 and CH3NHC3H7 metamers.
iv) No metamer for CH3OCH3.