In 1948 a Medical Student Definitely Determined That Cigarette Smokers

In 1948 a medical student definitely determined that cigarette smokers were 40X more likely to develop lung cancer. Since then,

A) Smoking has declined worldwide.
B) Scientists have found ways to cure lung cancer.
C) Smoking has declined in the United States, but not worldwide.
D) It's been determined that most people who die of lung cancer got it as a result of an infection, but smoking is still considered a risk.
E) Polluted air has replaced smoking as the primary cause of lung cancer.