Identify \(A\):

The correct answer is option 4.

Acetone can react with pyridine under acidic or basic conditions to form a condensation product. This reaction involves the removal of a water molecule from the combined molecules. Here, a new C-C bond forms between the carbonyl carbon of acetone and a carbon atom on the pyridine ring. The specific product depends on the position on the pyridine ring where the bond forms. The resulting condensation product (pyridyl/acetone adduct) then reacts with ethyl bromide to give pent-2-one.