The record of the past half century has established, I think, the two general principles about human disease. First, it is neces

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问题     The record of the past half century has established, I think, the two general principles about human disease. First, it is necessary to know a great deal about underlying mechanisms before one can really act effectively; one had to know that the pneumococcus (肺炎球菌) causes lobar pneumonia (球形肺炎) before one could begin thinking about antibiotics.
    Second, for every disease there is a single key mechanism that dominates all the others. If one can find it, and think one’s way around it, one can control the disorder. This generalization is harder to prove and arguable—it is more like a strong hunch (直觉) than a scientific assertion— but I believe that the record thus far tends to support it. The most complicated, multicell, multi-tissue, and multiorgan diseases I know are tertiary syphilis, chronic tuberculosis, and pernicious anemia. In each, there are at least five major organs and tissues involved, and each appears to be affected by a variety of environmental influences. Before they came under scientific appraisal, each was what we now call a "multifactorial disease. " And yet, When all the necessary facts were in it was clear that by simply switching off one thing—the spirochete, the tubercle bacillus, or a single vitamin deficiency—the whole array of disordered and seemingly unrelated pathological mechanisms could be switched off, at once.
The author uses the example of lobar pneumonia to show that________.

选项 A、understanding the cause of a disease precedes curing it
B、the record of the past half century is one of medical progress
C、antibiotics let to an understanding of underlying disease mechanisms
D、many diseases are now called multifactorial

答案A

解析 文中第一段第二句是个并列句,两个分句都含有“before”一词。第一个分句阐明第一条普遍原则,第二个分句进行了进一步的举例说明,即“人们在考虑使用抗生素之前,必须弄清肺炎球菌是引起球形肺炎的原因”。因此正确答案为A。
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