Which of the following is an example of a food source that pests may be attracted to?

The correct answer, grease traps, is a common food source that attracts various pests, particularly rodents and insects. Grease traps often contain food residues, grease, and other organic materials that provide a rich source of nutrition for pests. These traps are usually located in kitchens or food preparation areas, making them particularly appealing to pests looking for easy access to food.

Grease offers not just sustenance but also can help to create a conducive environment for pests to thrive; the warmth and moisture found in these areas can further entice them. The presence of grease and food remnants can effectively create a breeding ground for pests, leading to infestations if not properly managed.

Other options listed, like air ducts, underground tunnels, and outdoor gardens, do not primarily serve as direct food sources. While they can provide shelter or pathways for pests, they lack the nutrient-rich qualities found in grease traps that attract many pest species looking for food. Therefore, grease traps stand out as a direct and significant source of attraction for pests.