[简答题]

(46) For centuries the smoking of tobacco in cigarettes, cigars, and pipes has produced controversy over possible health hazards, but only since the 1950’s has sufficient scientific evidence accumulated to make possible a thorough evaluation of the health risk.
Scientific investigation of the relationship of smoking and health gained impetus after the beginning of the 20^th century, then an increase in lung cancer was noted. As the use of tobacco increased, studies improved. (47) Although some gaps in knowledge still exist, the information now available is sufficient to permit making sound judgments, based on the converging lines of evidence.
(48) Investigators have directed their principal consideration to cigarette smoking because the health consequences attributed to it far exceed those due to smoking cigars and pipes. The widespread popularity of cigarettes is comparatively recent in man’s use of tobacco. The smoking

B
People have smoked tobacco for centuries, and the harmful effects of tobacco smoke have been seen as controversial since at least the 16th century when European explorers introduced tobacco to North America. Cigarette, in fact, typically contains more than 4,700 chemical compounds, 43 of which are believed to cause cancer. Compounds such as tar and sulphur do most of the harm, whilst a poisonous compound known as nicotine makes smoking very difficult to give up.
In 1964, a committee of doctors and scientists in the United States of America concluded that nearly all forms of lung cancer were caused by the negative effects of smoking. They also reported, however, that smoking leads to many other diseases, such as chronic bronchitis and emphysema(disease of the lung). A more worrying report, however, argued that as many as 50,000 people die each year in America from the effects of passive smoking( breathing in other people’s
A. causes most forms of cancer
B. causes most forms of lung cancer
C. causes all forms of lung cancer
D. causes all forms of lung disease