A nurse is preparing to administer a medication to a client for motion sickness. Which of the following medications has therapeutic use in treating motion sickness?

The correct answer is D: Scopolamine (Scopace). Scopolamine is commonly used to treat motion sickness due to its ability to inhibit the signals in the brain that trigger nausea and vomiting. It is a muscarinic antagonist that works by blocking the action of acetylcholine. Furosemide (A) is a diuretic used to treat fluid retention, not motion sickness. Metformin (B) is an oral antidiabetic medication used to manage blood sugar levels. Naloxone (C) is an opioid antagonist used to reverse opioid overdose. Therefore, the correct choice for treating motion sickness among the options provided is Scopolamine.