Final answer:
The correct answer to the question is: D. methadone. Among the provided options, methadone is the exception, as it is not a Schedule IV-controlled substance but rather a Schedule II drug due to its higher potential for abuse.
Step-by-step explanation:
Schedule IV controlled substances are drugs with legitimate medical use but a lower potential for abuse and dependence compared to Schedule III drugs. Drugs classified under Schedule IV mainly include certain prescription medications.
Examples of Schedule IV substances include benzodiazepines, which are central nervous system depressants used for various conditions such as anxiety, seizure prevention, sedation, and insomnia. These include lorazepam (Ativan), alprazolam (Xanax), and clonazepam (Klonopin). Methadone, on the other hand, is a synthetic opioid commonly known for its use in the treatment of opioid dependence as well as for pain relief. It is classified as a Schedule II drug due to its higher potential for abuse and risk of severe psychological or physical dependence.