A 16-year-old boy suffering from drug abuse presents with cross-over of sensory perceptions, such that, sounds can be seen and colours can be heard. Which of the following is that most likely agent responsible for drug abuse

The characteristic features of acute LSD intoxication are perceptual changes occurring in a clear consciousness. These perceptual changes include depersonalisation, derealisation, intensification of perceptions, synaesthesias (for example, colours are heard, and sounds are felt), illusions, and hallucinations. In addition, features suggestive of autonomic hyperactivity, such as pupillary dilatation, tachycardia, sweating, tremors, incoordination, palpitations, raised the temperature, piloerection and giddiness, can also be present. Ref: A Sho Textbook of Psychiatry, Niraj Ahuja, 7th Edition, pg. no. 49