Question

Total number of isomers considering both structural and stereoisomers, of cyclic ethers with the molecular formula $C_4{H}_{8}O$ is:

Answer 1

One of the four membered cyclic struture exists as pair of enatiomers, contributing 2 to the total.
Two of the three membered cyclic structure exist as pair of enantiomers, contributing 4 to the total.
Also one of the three membered structures exhibits geometrical isomerism adding 1 to the total structure.