Final answer:
The best answer to the question is option (a) - 'Yes, they are not superimposable.' This selection accurately describes enantiomers, which are non-superimposable mirror images of each other.
Step-by-step explanation:
The compounds in question would be considered enantiomers if they are non-superimposable mirror images of each other. Enantiomers have unique properties in that they interact with polarized light differently, causing the light to rotate either to the left or to the right. This optical activity is directly related to the chiral centers in the molecule, typically carbon atoms with four different substituents. Therefore, the correct answer to whether two compounds are enantiomers if they are non-superimposable is 'Yes, they are not superimposable.' As such, the best answer is option (a).
Diastereomers, on the other hand, are also stereoisomers but are not mirror images of each other. Further distinguishing them, diastereomers have different chemical and physical properties, which can be observed in experimental settings.
For two molecules to be considered enantiomers, they must possess at least one chiral center with four different atoms or groups attached. This characteristic allows them to exist as two separate entities that are non-superimposable, much like left and right hands.