Which substance is tested for using Fast Blue B?

Fast Blue B is a dye that is primarily used in color tests to detect the presence of certain substances, particularly in forensic toxicology. It is specifically known for its effectiveness in identifying the presence of cannabinoids, which are the active components found in marijuana. When Fast Blue B is applied to a sample suspected of containing cannabinoids, it reacts to produce a characteristic color change, indicating a positive result for marijuana.

Cocaine, heroin, and nicotine, while important substances in the field of drug testing, do not yield positive results when tested with Fast Blue B. Each of these substances typically requires different specific testing methods or reagents uniquely tailored to detect their distinct chemical structures. Thus, the choice of Fast Blue B is uniquely suited for testing marijuana due to its selective interaction with cannabinoids, confirming the accuracy of the indicated correct answer.