The stereoisomers of a compound which are non-superimposable on each other are known as enantiomers. The molecule (A) has an asymmetric carbon atom. The mirror image of the molecule (i) and the 180° rotation are not superimposable on (A). The molecules (ii), (iii) and (iv) are superimposable on (A). The 180° rotation of the molecules (iii) and (iv) are superimposable on (A). Hence, the correct option is (i).