Monique cannot seem to sit still, talks rapidly, and never seems to get tired at the end of the day. Her friends suspect that she is taking:

a. cocaine.

b. Rohypnol.

c. LSD.

d. speed.

I think it is either c or d and I do know that it is not b.

To determine which substance Monique might be taking, let's analyze the options: cocaine, Rohypnol, LSD, and speed.

Cocaine: It is a stimulant drug that can increase energy levels, cause restlessness, and lead to rapid speech. However, it typically has a noticeable effect on the user's mood, causing euphoria or increased confidence, among other symptoms.

Rohypnol: Also known as a "date-" drug, Rohypnol is a sedative that can cause drowsiness, confusion, and memory loss. It is unlikely that Rohypnol is the substance Monique is taking because it does not match her symptoms of restlessness, rapid speech, and overall high energy levels.

LSD: Lysergic acid diethylamide (LSD) is a hallucinogenic drug that can distort sensory perceptions and alter thoughts, emotions, and overall perception of reality. While it may lead to increased energy levels during the drug's effects, the symptoms described by Monique's friends do not align with the typical effects of LSD.

Speed: Speed, also known as amphetamine, is a powerful stimulant drug. It can significantly increase energy levels, cause restlessness, lead to rapid speech, and a feeling of not getting tired. Given that Monique displays these characteristics, it is possible that she is taking speed.

Therefore, based on the symptoms described, the most likely answer is option d. speed. However, it is essential to note that this answer is purely speculative, and a professional assessment is necessary for an accurate diagnosis.