Identify the correct statement in the following :

Option (1): n-Butane and iso-butane are position isomers as only position of carbon is changed. Option (2): Dimethyl ether and ethanol are functional isomers as ether and alcohol are different functional groups. Option (3): Propan-l-ol and propan-2-ol are position isomers as only position of alcohol is changed. Option (4): Ethanoic acid and methyl methanoate are functional isomers as ester and acid are different functional groups.