An assistive device is effective only when it matches the patient's strength, balance, cognition, environment, and current task. A cane that is too tall, a walker placed too far ahead, or a transfer belt used around a new abdominal incision can create the fall it was meant to prevent. The registered nurse's work begins before equipment is handed over: identify why mobility changed, establish the safest level of assistance, and confirm that the patient can use the device consistently when tired, distracted, or symptomatic. The goal is not simply movement. It is safe participation with the greatest achievable independence and the least preventable harm. On the exam, writers often pair stable-sounding options with unstable data—notice the mismatch before you commit. If the stem names a license or role, reread that line; scope errors are classic trap answers even when the clinical topic is familiar. Run a 60-second scan: breathing work and oxygenation, perfusion and end organs, neuro baseline, likely infection sources, and devices that can fail quietly. When two answers feel partly right, pick the one that reduces imminent harm...