求助一道让我非常迷惑的GWD题!!

pychina

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 have medical conditions that are much less serious than appendicitis

b   the misdiagnoses produced by this test are always 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 答案是b,为什么呢

jkshen

最重要的最后一句话:Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since ______. 使用这种测试，医生可以大大减少不必要的阑尾手术, 但也减少了必要的手术。（要移除的没移除)

B 就是对这层意思的解释。