Which of the following can be used as a ratchet in a rescue system?

The Prusik hitch is a climbing knot used to create a friction hitch on a rope, making it an effective ratchet in rescue systems. When tied correctly, a Prusik hitch can slide freely when heavy loads are not applied but will hold fast when weight is introduced, effectively acting as an anchor point or a means to progress along a rope. This functionality allows rescuers to ascend or descend securely while managing the load of a victim or equipment.

In contrast, options like a rappel device serve to facilitate controlled descents and ascents but do not provide the same secure locking mechanism under load that a Prusik hitch does. A static line refers to a rope that does not stretch much under load, and while it is crucial for safety and stability, it lacks the ratcheting capability provided by the friction created in a Prusik hitch. Lastly, a rescue blanket is primarily used for shielding or protecting a victim, rather than for any mechanical advantage or load management in a rescue system. Hence, the unique properties of the Prusik hitch equip it to function effectively as a ratchet in various rescue scenarios.