Final answer:
Marlo most likely took a hallucinogen, which is known for causing profound perceptual distortions and feelings of alertness.
Step-by-step explanation:
Based on the description that Marlo has taken a drug that produced dramatic perceptual distortions and a feeling of alertness, the most likely type of drug Marlo took would be a hallucinogen. Hallucinogens are known for causing profound changes in sensory and perceptual experiences, which can include visual and sensory hallucinations, as well as altered perceptions of the passage of time and a change in consciousness. While stimulants also increase alertness, they do not typically produce the dramatic perceptual changes associated with hallucinogens. Therefore, the correct answer is D. Hallucinogen.