Which of the following is NOT considered a dangerous substance?

Over-the-counter (OTC) medications are generally not classified as dangerous substances in the same way that controlled substances or prescription medications are. OTC medications are readily available to consumers without the need for a prescription, which indicates that they are considered safe for self-medication when used according to the directions provided.

In contrast, substances categorized as C1 are considered highly dangerous due to their potential for abuse, severe dependence, and lack of accepted medical use in the United States. Prescription medications often also include dangerous substances, as they require a healthcare provider's authorization for use due to the risks associated with their use. Similarly, controlled substances as defined by the FDA, which include both C1 and other scheduled drugs, are tightly regulated because of their potential for abuse and dependence.

Thus, the classification of OTC medications as non-dangerous substances in this context reflects their regulated availability and the belief that they can be safely used as directed by consumers without professional supervision.