Which of the following is a common street name for cocaine?

The common street name for cocaine is "Crack." This term specifically refers to a form of cocaine that has been processed to create a crystal or rock-like substance. Crack cocaine is typically smoked, which allows for an intense and immediate high. The name "crack" comes from the crackling sound it makes when heated.

The other terms listed do not accurately represent cocaine. "Euphoria" refers to an intense feeling of happiness and is not a specific street name for any drug. "Xanax" is the brand name for alprazolam, a medication used to manage anxiety and panic disorders, which is not related to cocaine. "Fast" does not correspond to any known street name for cocaine. Understanding these distinctions is crucial for recognizing the various forms and names associated with illicit drugs.