A food sample was tested with Fehling's solution and produced a brick-red precipitate. Which of the following substances is most likely present in the sample?

Fehling's solution is used to detect reducing sugars such as glucose and maltose. A positive result is indicated by the formation of a brick-red precipitate of copper(I) oxide. Starch is detected by iodine solution, proteins by the Biuret test, and lipids by the emulsion test.