[单项选择]There are only three available strategies for controlling cancer: prevention, screening and treatment. Lung cancer causes more deaths than any other types of cancer. A major cause of the disease is not【C1】______known; there is no good evidence that screening is much help; and treatment fails in about 90 percent of all cases. At present, therefore, the main strategy must be【C2】______. This may not always be true, of course, as for some other types of cancer, research over the past few decades has produced(or suggested)some importance in prevention, screening or treatment. 【C3】______however, we consider not what researcher may one day offer but what today"s knowledge could already deliver that is not being delivered, then the most practical and cost-efficient opportunities for avoiding premature death from cancer, especially lung cancer, probably involve neither screening nor improved【C4】______. but prevention. This conclusion does not depend on the unrealistic assumption that we can eliminate tobacco. It merely assumes that we can reduce cigarette sales appreciably by raising prices or by【C5】______on the type of education that already appears to have a positive effect on cigarette assumption by white-collar workers and that we can substantially reduce the amount of tar【C6】______per cigarette. The practicability of preventing cancer by such measures applies not only in those countries, such as, the United States of America, because cigarette smoking has been common for decades, 25 to 30 percent of all cancer deaths now involves lung cancer, but also in those where it has become【C7】______only recently. In China, lung cancer as yet accounts for only 5 to 10 percent of all cancer deaths. This is because it may take as much as half a century for the rise in smoking to increase in the incidence to lung cancer. Countries where cigarette smoking is only now becoming widespread can expect enormous increase in lung cancer during the 1990"s or early in the next century,【C8】______prompt effective action is taken against the habit-indeed, such increase are already plainly evident in parts of the world. There are reasons why the preventions of lung cancer is of such overwhelming importance: first, the disease is extremely common, causing more deaths than any other types of cancer now【C9】______: secondly, it is generally incurable; thirdly, effective, practicable measures to reduce its incidence are already reliably known; and finally, reducing tobacco consumption will also have a substantial【C10】______on many other diseases.【C7】
A. sensitive
B. tight
C. widespread
D. rough