We are looking for an answer that explains how the second set of recommendations and its results strengthen the doc’s first hypothesis: the first prescribed dosage did not help the patient because it was too low.
(B) tells us that they support this first hypothesis by making it LESS plausible that the beverage contributed to the medication not working.
If anything, the sequence of events would tend to show that the beverage MAY have contributed to the medication not working.
When the patient took the first higher dose while consuming the beverage, there was no relief. However, when the beverage was stopped and the patient took the higher dose the second time, she had success.
Removing the variable (“the beverage”) and seeing the effect disappear (“medication NOT working at higher dose”), if anything, would make it more plausible that the beverage in some way contributed to the medicine not working.
The doc’s initial hypothesis is that the first dosage is not enough to be effective for the patient. When it is learned that a beverage may be interfering with the efficacy of the medication, the doctor starts his second set of recommendations:
First, the patient tries the lower dosage again without the beverage. The medicine is not effective.
Then, the patient tries the higher dosage again without the beverage. This time the medicine is effective.
Showing that the lower dosage still did not work even without the consumption of the beverage supports the doc’s first claim by showing that something other than the beverage must have caused this first dosage to not work. After all, if it were only the beverage preventing the lower dosage from working, then when the “beverage variable” was removed during the second set of recommendations, the lower dosage would have worked.
Since the lower dosage did not work even when the patient did not drink the beverage and the medicine only worked when the dose was raised, this supports the doc’s first claim by showing that the beverage was not the only cause for the lower dose not working ——-> thereby making it more likely that another cause was at play (such as the dose being too low).
By ruling out the possibility that the beverage was the only thing preventing the lower dose from working, the second set of recommendations and its results tend to support the doc’s first claim that the initial dose was too low.
Thus, (D) explains this best.
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