Which of the following substances is also known as acid?

The correct answer is LSD, which is often informally referred to as "acid." This term stems from the substance's chemical structure, which includes lysergic acid diethylamide. LSD is a powerful hallucinogenic drug that affects an individual's perception, mood, and cognitive processes.

LSD gained popularity in the 1960s and is well-known in both recreational and counterculture contexts. The nickname "acid" emphasizes its properties and has become widely recognized in discussions about drugs.

The other substances listed—cocaine, marijuana, and hashish—do not share this same association. Cocaine is a stimulant and is derived from the coca plant, while marijuana and hashish are both cannabis products, primarily known for their psychoactive compound THC. Hence, the terminology and characteristics associated with LSD as "acid" underscore its unique place in the category of psychoactive drugs.