Which of the following drugs is classified as Schedule I?

Schedule I drugs are substances that are considered to have a high potential for abuse, have no currently accepted medical use in treatment in the United States, and lack accepted safety for use under medical supervision. LSD (lysergic acid diethylamide) fits all these criteria. It is a powerful hallucinogenic drug that is not accepted for any medical use and is recognized for its high potential for abuse.

In contrast, cocaine, morphine, and codeine are classified as Schedule II drugs. Schedule II substances have a high potential for abuse but also have accepted medical uses, albeit with strict regulations surrounding their prescription and distribution. Morphine and codeine are both opioid analgesics used for pain management, while cocaine has limited medical uses such as a local anesthetic in certain surgical procedures.

Therefore, LSD is accurately classified as a Schedule I drug, reflecting its stringent regulation due to its high potential for abuse and lack of medical application.