Until the middle of the 20th century, doctors sometimes suggested that people smoke in order to reduce stress. Since then, doctors have been asking
patients who smoke to quit.
What caused this change?
A. Studies have shown that tobacco and tar in cigarettes have
negative health effects.
B. Tobacco is an illegal drug, and doctors are required to discourage
its use.
C. Tobacco is a nonrenewable resource, and the government has
restricted its use.
D. Tobacco plants have been categorized as an endangered species,