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题库 / GMATLA-CR-73
Which of the following most logically completes the passage?
Appendicitis (inflammation of the appendix) is potentially fatal; consequently, patients with symptoms strongly suggesting appendicitis almost always have their appendix removed. The appropriate surgery is low-risk but performed unnecessarily in about 20 percent of all cases. A newly developed internal scan for appendicitis is highly accurate, producing two misdiagnoses for every 98 correct diagnoses. Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since ______.
the patients who are correctly diagnosed with this test as not having appendicitis invariably have medical conditions that are much less serious than appendicitis
the misdiagnoses produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it
all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis
every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms generally associated with appendicitis
the only patients who are misdiagnosed using this test are patients who lack one or more of the symptoms that are generally associated with appendicitis
达到的目标：1）unnecessary的手术减少了。2）necessary的手术没有减少。
b选项说误判的情况都是把没病的人判断成为弄成有病了，也就是说导致了unnecesary的情况，所以误判的情况全部都是unnecessary（没病说成有病）,所以necessary的都没有被判错，所有有病的人都被判断出来了，因此2）条件成立了，然后看到原文说之前是20%误判unnecessary，现在变成了2%误判unnecessary，所以1）条件也成立，unnecessary的手术减少了。
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