Which of the following items could be considered an expedient perimeter barrier?

An expedient perimeter barrier is often characterized by its simplicity, ease of deployment, and effectiveness in providing immediate security. Ropes can serve this purpose by being quickly set up to create a physical boundary, signaling to individuals that access is restricted. They are flexible, lightweight, and can be easily manipulated to fit various situations, making them a viable option for temporary or improvised security measures at an entry point or perimeter.

Barricades, while effective, typically require more substantial resources and preparation to implement. Security personnel provide a human presence but do not function as a physical barrier on their own. Automated gates, although very secure, usually involve a greater investment and cannot be classified as "expedient" in scenarios requiring quick or temporary solutions. Thus, ropes stand out as the most suitable choice for creating an immediate and simple perimeter barrier.