Which of the following substances is NOT classified under Schedule IV?

The correct answer is C, Fentanyl, because fentanyl is classified under Schedule II of the controlled substances list. Schedule II substances are those that have a high potential for abuse and can lead to severe psychological or physical dependence. Fentanyl is a powerful opioid used medically for pain management but is also associated with a high risk of addiction and overdose, which is why it falls into this stricter category.

In contrast, substances like Diazepam, Alprazolam, and Phentermine are classified under Schedule IV. This schedule includes drugs that have a lower potential for abuse relative to those in higher schedules and are considered to have accepted medical uses. Although they still carry some risk of dependence, they are generally viewed as safer and less addictive compared to Schedule II substances like fentanyl. Consequently, this classification reflects the varying levels of risk associated with each substance.