Optical isomers which are non-superimposable mirror images of each other are called

• Optical isomers are two compounds that have distinct spatial arrangements of the atoms, the same number and types of atoms, bonds (i.e., the connectivity between atoms is the same), and the same bonds, but which do not have superimposable mirror images.
• Enantiomers are a pair of stereoisomers that cannot be superimposed on one another. This indicates that they are molecules made up of identical atoms that are bound together in the same way, i.e., they have the same connectivity.

Hence, the correct option (A).  Enantiomers