Tar's Role in Causing Lung Cancer via DNA Damage

Steps:

• Identify tar as a component of cigarette smoke containing carcinogens that enter lungs.
• Trace how carcinogens interact with lung cells' DNA.
• Link DNA damage to mutations that disrupt cell growth control.
• Evaluate choices for accurate sequence of cancer development.

Why A is correct:

• Carcinogens in tar bind to DNA, causing mutations that lead to uncontrolled cell division, as defined in carcinogenesis pathways.

Why the others are wrong:

• B: Describes mucus response and phagocyte attraction, which relates to irritation, not tar's primary carcinogenic effect.
• C: Sequence is incomplete and garbled; accumulation leads to inflammation but not directly to alveolar destruction from tar.
• D: Reverses mutation and immune response; phagocytes respond after, not before, mutations.

Final answer: A