Chemistry · Acids, Bases and Salts

A student takes four test tubes labeled A, B, C, and D, each containing a colorless liquid. She adds a few drops of phenolphthalein indicator to each: - In test tubes A and C, the solution turns pink. - In test tubes B and D, the solution remains colorless. She then adds excess dilute HCl to all four test tubes and notes that all solutions become colorless. What can be concluded about the initial nature of the solutions?