Which of the following drugs is classified as a Schedule II substance?

The classification of drugs into schedules is based on their potential for abuse, accepted medical use, and the degree of dependence they may cause. Morphine is classified as a Schedule II substance because it has a high potential for abuse, which can lead to severe psychological or physical dependence. Despite the risks, morphine has accepted medical uses, primarily in the management of severe pain, which is a crucial aspect of its Schedule II classification.

In contrast, ibuprofen is a non-steroidal anti-inflammatory drug (NSAID) that is generally available over the counter and is not classified as a controlled substance. Lorazepam and clonazepam are classified as Schedule IV substances, indicating a lower potential for abuse and lower risk of dependence in comparison to Schedule II drugs. Thus, morphine stands out as the correct answer, fitting the criteria for Schedule II substances.