Which of the following is considered a part of mechanical advantage systems?

The correct choice is pulleys, as they are essential components of mechanical advantage systems. Mechanical advantage refers to the ability to lift or move a load with less effort by using a system that distributes the weight and forces involved. Pulleys serve this purpose by redirecting the force applied to a rope, which can multiply the force output.

When you incorporate one or more pulleys into a rescue system, you significantly reduce the effort required to lift a load, making it easier for rescuers to perform operations in challenging surface water conditions. This system is critical in rescue operations where manpower is limited, and the efficiency of lifting or moving a person or object can be crucial.

The other options listed—throw ropes, tag lines, and tether lines—serve different purposes in rescue scenarios, such as securing a line to guide a rescuer or victim, assisting in reach and retrieval, or providing safety and control, but they do not contribute to the mechanical advantage principle that pulleys do. Therefore, pulleys are specifically designed to enhance lifting efficiency, distinguishing them as the correct answer in this context.