Choice A rationale Morphine is a potent opioid analgesic commonly prescribed for moderate to severe pain. A dosage of 4 mg intravenously every four hours as needed for pain is within the typical therapeutic range for post-operative pain management, and the frequency allows for sufficient time between doses to assess the analgesic effect and minimize accumulation. Choice B rationale Hydromorphone is a very potent opioid, significantly stronger than morphine. A dosage of 2 mg intravenously every two hours for severe pain is a high dose and a relatively short interval. This combination increases the risk of opioid toxicity, including respiratory depression and profound sedation, necessitating verification with the prescribing provider. Choice C rationale Ondansetron is a serotonin receptor antagonist used to prevent and treat nausea and vomiting. A dosage of 4 mg orally every eight hours as needed for nausea is a standard and safe therapeutic dose, commonly employed in the post-operative setting to manage emesis with minimal adverse effects. Choice D rationale Docusate sodium is a stool softener that works by increasing water and fat penetration into the stool, making it easier to pass. A dosage of 240 mg orally daily as needed for constipation is a common and appropriate dose for preventing and managing post-operative constipation, which is a frequent side effect of opioid analgesics.