Final answer:
The correct method for denying pests access to an operation is to use screens on vents, creating a physical barrier that prevents their entry and maintains a hygienic environment.
Step-by-step explanation:
In answering the question regarding methods of denying pests access to operations, option C) use screens on vents is correct. This is a common and effective method for preventing flying insects and other pests from entering buildings and areas where food is processed or stored. By installing screens on windows, doors, and vents, physical barriers are created that block pests from coming inside, thereby ensuring a hygienic environment that is critical for health and safety in food operations.
Other measures that are commonly used in integrated pest management include maintaining cleanliness to avoid attracting pests, storing food properly, and careful waste disposal. However, the options of providing free food, eliminating all cleaning measures, and leaving doors open would all counteract pest control efforts and are therefore incorrect responses to this question.