Thanks for the question! So back to a recap of the stimulus, we’re being told here that the patient’s suffering from X or Y, but we don’t know which. So since there’s an effective treatment for Y but not X, we should assume that the patient has Y.
Now the question’s asking us for a principle that we could base the physician’s reasoning on. And (A) tells us that this principle is that in treating a patient who has one of two diseases (but we don’t know which), it’s more important to treat the diseases than to determine which of the two diseases the patient has. But if the patient has X and the doctor uses the Y treatment, the disease won’t be treated. And the conclusion is basically about assuming that the patient has Y, and (A) doesn’t tell us why we should assume that the patient has Y. Because it doesn’t help justify the specific conclusion here, it’s not the right answer choice.
Hope this helps! Feel free to ask any other questions that you might have.
