What type of item must be loaded securely to prevent hazards in flight?

The correct choice identifies dangerous goods as items that must be loaded securely to prevent hazards in flight. Dangerous goods are materials that pose a risk to health, safety, property, or the environment, often because they are flammable, explosive, toxic, or corrosive. Proper handling and secure loading are critical for these items to mitigate any potential risks during the flight, ensuring the safety of the aircraft, crew, and passengers.

In contrast, while documents, food items, and clothing can and should be secured to prevent movement and ensure safety, they do not carry the same level of risk as dangerous goods. Documents and clothing typically do not pose a fire, explosion, or health hazard like dangerous goods can, and food items, though needing some care, usually do not have the same stringent regulations regarding their transport. This distinction emphasizes the importance of proper procedures for dangerous goods to avoid any serious incidents during air travel.