Answer : The correct option is, Isomers
Explanation :
Isotope : It is defined as the element that have the same number of protons but have the different number of neutrons of each of the atom.
Functional groups : It is defined as they are specific grouping of atoms within the molecule that have their own characteristic properties.
For examples : alcohols, amines, carboxylic acids, ketones, ethers etc.
Hydrocarbons : It is defined as the type of organic compound that contains only hydrogen and the carbon atoms.
Enantiomers : When the two stereoisomers differ only in their arrangement of atoms and groups in space and exhibit non-superimposable object mirror image relationship.
Isomer : It is defined as a molecule have the same molecular or chemical formula but the different chemical structure or shape.
For example :
There are three structural isomers of n-hexene that is based on the location of the double-bonded carbon atoms with the other atoms.
In n-hexane, 'n' shows that the chain should be straight chain there is no branching.
The three structural isomers of n-hexene are, 1-hexene, 2-hexene and 3-hexene.
Hence, the correct option is, Isomers