The ketone shown is stirred with sodium ethoxide in ethanol at $25^{\circ }$C (equilibrating conditions) and then treated with benzyl bromide. Which structure shown is the major C-alkylation product?

The ketone shown is 2-methylcyclopentanone. A weak base at room temperature lets the enolates equilibrate, so the more stable, more substituted (tetrasubstituted) thermodynamic enolate predominates. Its C-alkylation with benzyl bromide at C2 gives 2-benzyl-2-methylcyclopentanone, a quaternary centre; the kinetic product, the O-alkylation product and the dialkylated product are not the major compound.