Treatment of (S) - () - 5-methyl-2-cyclohexenone with lithium dimethylcuprate gives, after protonolysis, a good yield of a mixture containing mostly a dextrorotatory ketone A and a trace of an optically inactive isomer B. Treatment of A with zinc amalgam and HCl affords an optically active, dextrorotatory hydrocarbon C. Identify compounds A, B, and C, including stereochemical configurations. Be sure to explicitly draw H and both wedge/dash bonds at any configuration center.