Ans B

Gist of the stem :
--Patients with strong appendicitis symptoms undergo surgery
--about 20% of all cases the surgery is not needed
--New Test developed is highly accurate and it produces only 2 misdiagones for every 98 correct diagoses
--doctors can largely avoid unnecessary appendicitis surgery without performing any fewer necessary ones than before.

Concentrate on the last line.
the doctors will not reduce performing the surgery on necessary patients ..Y ? becoz the m/c diagnoses correctly the patients who need to undergo surgery but the m/c might misdiagnose patients who do not need surgery (2 out of the 98)

The answer choice should depict the explanation that

Clearly, using this test, doctors can largely avoid unnecessary removals of the appendix without, however, performing any fewer necessary ones than before, since the m/c misdiagnosed only cases which did not need surgery .

From the answer choices

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 (Wrong:We are not bothered about any other medical condition)
B. the misdiagnoses produced by this test are always instances of attributing appendicitis to
someone who does not, in fact, have it (Correct : no necessary surgeries were skipped as the m/c performance is accurate. there was no decrease in correct surgeries being performed as the m/c inaccurately determines patients who do not need the surgery only)
C. all of the patients who are diagnosed with this test as having appendicitis do, in fact, have appendicitis ( Wrong: this is what the last line says we need additional info ,a follow up )
D. every patient who is diagnosed with this test as having appendicitis has more than one of the symptoms generally associated with appendicitis ( Wrong :we need a follow up for correct cases were not decreased)
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
(In this case the correct surgeries should have decreased which did not happen )