Which of the following is a method for preserving food?

Canning is a method for preserving food that involves sealing food in airtight containers and heating them to a temperature that kills harmful bacteria and enzymes. This process allows food to be stored for long periods without refrigeration. The heating destroys microorganisms that can cause spoilage, while the sealed environment prevents new organisms from entering. Furthermore, canning helps in retaining the food's nutritional value, flavor, and texture, making it a popular choice for preserving fruits, vegetables, meats, and more.

In contrast, boiling, frying, and baking are primarily cooking methods rather than preservation techniques. Boiling involves cooking food in water or broth, which does not necessarily prevent spoilage after the food is cooled. Frying cooks food in oil, also not providing a means to preserve it long-term. Baking is a dry heat method used to prepare dishes and can alter textures and flavors, but it does not have the same preservation qualities that canning offers. Overall, canning stands out as an effective means of extending the shelf life of food.