求思路

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 ______.

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

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

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

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

        
5. 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

B 是对的啦。

其实这个题目的关键是最后那句话 without, however, performing any fewer necessary ones than before。

要做完这个TEST 后，UNNECESSARY 的手术，大幅减少，同时， NECESSARY 的手术不减少。

唯一的情况就是， B， 误诊的那两个人，实际上是没有APPENDICTIS 的。 也就是说只有在这种情况下，才可以做到，without, perporming any fewer necessary ones than before.

而C 呢，只说明了，确诊的人都是对的，即他们如果有这个病，测验结果就是有病。但是误诊的那2%呢？并没有说。如果误诊的那两个人，是本来有病，却被误诊为没病（正好与B 相反，也是得出结论最关键的一点）。那么就达不到，题目的结论，也就是最后，最关键那句话，即，without, however, performing any fewer necessary ones than before，因为那个手术本来是要做的，病人本来是有病的，却没有手术。

说白了就是，要把没病的查成有病（B 答案），也不能把有病的查成没病的（C 为排除这个成立的可能性）

DOES IT MAKE SENCE？