The correct option is B i-C, ii- B, iii- A, iv-D
(i) Racemisation takes place in SN1 reaction.
(ii) Alkylidene halides are named as gemdihalides. In gemdihalides halogen atoms are present on same carbon atom.
(iii) In vicinal dihalides, halogen atoms are present on the adjacent carbon atom. Bromination of alkenes will give vicinal dihalides.
(iv) Elimination of HX from allrylhalide follows Saytzeff rule.