Effects of cigarette smoke components on the body

Steps:

• Identify carbon monoxide's action: binds to hemoglobin, forming carboxyhemoglobin and reducing oxygen delivery.
• Identify nicotine's action: acts as a stimulant, exciting nerve endings and increasing heart rate.
• Identify tar's action: contains carcinogens that damage lung tissue and promote cancer.
• Compare options to these known effects to select the matching one.

Why D is correct:

• Matches definitions: carbon monoxide competes with oxygen for hemoglobin binding sites (per gas physiology); nicotine mimics acetylcholine to stimulate nicotinic receptors on nerve endings; tar includes polycyclic aromatic hydrocarbons, known carcinogens per toxicology.

Why the others are wrong:

• A: Carbon monoxide does not stimulate nerves; nicotine narrows bronchi, not arteries; tar causes emphysema, not directly obstructive disease.
• B: Nicotine does not increase clots; tar does not block goblet cells, which produce mucus.
• C: Carbon monoxide does not raise blood pressure; nicotine does not bind hemoglobin; tar does not increase clot risk.

Final answer: D