Nicotine is addictive and is the only known psycho- active ingredient in tobacco smoke.

The statement has two parts: (1) nicotine is addictive - TRUE, and (2) it is the ONLY known psychoactive ingredient in tobacco smoke - this is more complex. Tobacco smoke contains other psychoactive substances including MAO inhibitors (harman and norharman) which enhance nicotine's addictive effects. However, nicotine is indeed the PRIMARY and most significant psychoactive ingredient, and its addiction mechanism is well-established. In the context of basic health education, this statement is generally accepted as true, as nicotine is the main driver of tobacco addiction.