A and B in the following reactions are (a) (b) (c)

The compound given in the reactant is a ketone. So, when the HCN group attacks the ketone and the hydrogen group will get attached to the oxygen atom. The cyanide group will attach to the carbon atom. So, this compound is reduced using a strong reducing agent like 퐿푖퐴푙퐻4, the cyanide group will convert into 퐶퐻2푁퐻2.