Final answer:
The correct answer is 'a) Canning; drying,' where canning can preserve foods for several years by keeping them sealed from air and microbes, while drying removes moisture to inhibit microbial growth but may not extend shelf life as long.
Step-by-step explanation:
Canning; drying preserves foods for a few years, unlike drying, which may not have as long a shelf life. This is because canning effectively seals products away from the oxygen and microbes that cause spoilage.
Preservation methods like canning and drying serve to protect foods from microbial growth and spoilage. Canning is a process where foods are processed and sealed in an airtight container, extending the shelf life for several years by preventing contact with microbes and oxygen. Drying, on the other hand, or desiccation, removes moisture from foods, which is necessary for microbial metabolism and survival, but may not kill all microbes. When water is restored, surviving microbes may potentially regrow. Dried foods are preserved because of the reduced water activity, sometimes accelerated by adding substances such as sugar or salt, which bind to water molecules, thereby making less water available to support microbial life.
These methods are examples of how food preservation techniques leverage biological principles such as osmotic pressure and microbial inhibition to keep food edible over extended periods. While drying tends to be suitable for shorter periods, canning can keep food preserved for several years in a stable state, contributing to food security and reducing waste.