4

5

6

7

Iso−pentane and neo−pentane

Glucose and fructose

Ethanol and dimethyl ether

α−Naphthol and β−Naphthol

9 sigma bonds, 1 pi bond and 2 lone pairs

8 sigma bonds, 2 pi bonds and 2 lone pairs

10 sigma bonds, 1 pi bond and 1 lone pair

9 sigma bonds, 2 pi bonds and 1 lone pair

n−butane

2,4−dimethyl pentane

Benzene

None of the above

Position isomerism

Optical isomerism

Functional isomerism

All of the above