The correct answer is option 2: prevention of entry of diseased organisms. Quarantine regulations are policies and procedures implemented to prevent the introduction and spread of diseases, pests, and other harmful organisms. These regulations aim to control the movement of goods, animals, and people that may carry or be infected with diseases or pests. By preventing the entry of diseased organisms, quarantine regulations help protect the health and safety of plants, animals, and humans. This is done by conducting inspections, establishing strict import/export controls, requiring certifications and permits, and implementing measures such as disinfection and fumigation. Quarantine regulations are an important aspect of biosecurity and play a crucial role in safeguarding agriculture, ecosystems, and public health.