Answer:
a.Carcinogen, any of a number of agents that can cause cancer in humans. They can be divided into three major categories: chemical carcinogens (including those from biological sources), physical carcinogens, and oncogenic (cancer-causing) viruses.
b.a toxic colorless or yellowish oily liquid that is the chief active constituent of tobacco. It acts as a stimulant in small doses, but in larger amounts blocks the action of autonomic nerve and skeletal muscle cells. Nicotine is also used in insecticides.
c.a colorless volatile flammable liquid that is produced by the natural fermentation of sugars and is the intoxicating constituent of wine, beer, spirits, and other drinks, and is also used as an industrial solvent and as fuel.
d.a habit-forming drug that, while not itself addictive, may lead to the use of other addictive drugs.
"many believe that alcohol and cigarettes are gateway drugs that increase the risk of subsequent involvement with illegal drugs"
e.Drug dependence occurs when you need one or more drugs to function. The American Psychiatric Association (APA) used to distinguish between dependence and abuse. Abuse was considered the mild or early phase of inappropriate drug use that led to dependence. People viewed dependence as a more severe problem than abuse.
