Palm wine turns sour with time because?

Palm wine turns sour with time because of microbial activity that occurs within it. Microorganisms such as bacteria and fungi that are naturally present in the environment and in the sap of the palm tree can enter the palm wine during tapping and fermentation. These microorganisms metabolize the sugar present in the palm wine, producing organic acids such as lactic acid and acetic acid, which give the wine a sour taste. The longer the palm wine is left to ferment, the more pronounced the sour taste becomes as more and more organic acids are produced. Therefore, option d, "microbial activity results in the production of organic acids within it" is the correct answer.