Which of the following is an example of a natural food preservative?

Natural food preservatives are substances derived from natural sources that help extend the shelf life of food by inhibiting the growth of bacteria, fungi, and other microorganisms. In this case, all the options presented—sugar, salt, and vinegar—are effective natural preservative agents.

Sugar acts as a preservative by creating a hypertonic environment. When sugar is added to foods, it draws moisture out through the process of osmosis, which inhibits the growth of bacteria and molds that thrive in moist environments.

Salt preserves food primarily by drawing moisture out and creating an environment that is less hospitable to microorganisms. This method is traditionally used in curing meats and in pickling vegetables.

Vinegar, which is an acetic acid solution, lowers the pH of foods, making it difficult for spoilage bacteria to survive. This is why vinegar is often used in pickling.

Therefore, since sugar, salt, and vinegar all function as natural preservatives by employing different mechanisms to inhibit microbial growth, the correct answer includes all of these options.