一道机井求助

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________________

a: the patients who are correctly diagnosed with this test as not having appendicitis invariably having medical conditions that are much less serious than appendicitis

b: the misdiagnoses produced by this test are always instances of attributing appendicitis to someone who does not, in fact, have it

c: all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis

d: every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms generally associated with appendicitis

e: 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 (2004.04.26)

选D对不对？请各位大虾帮忙！

应为B。

关键是理解结论：不必要的手术大大减少，必要的手术却没减少。（必要的手术指必须去掉A）。后面要完成的部分解释为何必要的手术没减少。B说误诊断的总是将没有A的诊断成有A。也就是有A（必须做手术）的都断出来，还有一点（根据原文是2%）没有A的也诊断成有A。所以必要的手术并没减少。故B为答案。

D属于无关选项，因为文中没有symptoms 这个概率；

而且C、D、E的副词all、every、only都是明显的错误选项特征，对于这道题目来说。

A完全说的是另外的事情，更不能选。