Step-by-step explanation:
The correct answer is:
d) nicotine.
Nicotine is the colorless, oily addictive compound found in cigarette smoke. It is a naturally occurring chemical found in the tobacco plant. When tobacco is smoked, nicotine is released and inhaled into the lungs, where it is rapidly absorbed into the bloodstream. Nicotine acts as a stimulant and is highly addictive, making it one of the primary reasons why smoking is difficult to quit.