How can micro-organisms be introduced to food?

Micro-organisms can be introduced to food through various sources, including soil, humans, and pests. This reflects the diverse ways that contamination can occur. Soil can carry bacteria, viruses, and fungi that may transfer to food during farming or harvesting. Humans, through improper handwashing, can transfer pathogens directly to food items, especially during food preparation or handling. Additionally, pests, such as insects and rodents, often carry harmful micro-organisms and can contaminate food through droppings, saliva, or by directly accessing food sources.

The other options present more limited scenarios. Packaging alone does not typically introduce micro-organisms; it is generally designed to protect food from contamination but can also be a source of contamination if not handled properly. Stating that contamination occurs only from pests and rodents excludes other significant factors, such as soil and human contact. Lastly, washing with water can help remove some contaminants but may not eliminate all micro-organisms, and if water is contaminated, it can actually introduce further pathogens to food. Thus, the correct answer encompasses a broad and realistic view of the many ways micro-organisms can be introduced into food.