A _________________ drug is one which precedes the use of illegal or illicit drugs.HarmlessGatewayPrescriptionTobacco-based

The term you are looking for is "Gateway."

A gateway drug is typically considered a substance that is believed to lead users to try more dangerous or illicit drugs. Often, gateway drugs are legal substances that could include alcohol, tobacco, or marijuana. The idea is that by trying these less harmful substances, individuals may develop a habit or an inclination to seek out more potent and harmful drugs as they continue to experiment. This term has been a topic of debate among researchers, as it raises questions regarding addiction and risk factors associated with drug use. Many health experts argue that while gateway drugs might influence later drug use, a variety of factors including social environment, mental health, and genetics also play a significant role in the progression towards heavier drug use.