Critical Reasoning

A new drug, taken twice daily for one month, is an effective treatment for a certain disease. The drug now most commonly prescribed for the disease occasionally has serious side effects such as seizures; the new drug has side effects much more frequently, but the worst of them is mild nausea. Therefore, the new drug is clearly preferable as a treatment.

Which of the following, if true, most seriously weakens the argument?

A) It is possible that the drug now most commonly prescribed has side effects that have not yet been attributed to it.
B) People who experience nausea are prone to discontinue use of the new drug prematurely.
C) Other drugs for the disease have typically been prescribed only for patients allergic to the most commonly prescribed drug.
D) People who have received effective treatment for disease do not generally contract the disease again.
E) There is a nonprescription medication that when taken with the new drug prevents the onset of nausea.

OA:B

Source:GMATPrep EP2

NandishSS wrote:A new drug, taken twice daily for one month, is an effective treatment for a certain disease. The drug now most commonly prescribed for the disease occasionally has serious side effects such as seizures; the new drug has side effects much more frequently, but the worst of them is mild nausea. Therefore, the new drug is clearly preferable as a treatment.

Which of the following, if true, most seriously weakens the argument?

A) It is possible that the drug now most commonly prescribed has side effects that have not yet been attributed to it.
B) People who experience nausea are prone to discontinue use of the new drug prematurely.
C) Other drugs for the disease have typically been prescribed only for patients allergic to the most commonly prescribed drug.
D) People who have received effective treatment for disease do not generally contract the disease again.
E) There is a nonprescription medication that when taken with the new drug prevents the onset of nausea.

Premise: While the most commonly prescribed drug occasionally has serious side effects, the worst -- although much more frequent -- side effect of the new drug is mild nausea.
Conclusion: The new drug is clearly preferable as a treatment.

To weaken the conclusion, the correct answer choice must show that the new drug is NOT better than the most commonly prescribed drug.

B: People who experience nausea are prone to discontinue use of the new drug prematurely.
Here, the mild nausea frequently caused by the new drug is likely to induce many people to stop taking the drug, WEAKENING the conclusion that the new drug is better than the most commonly prescribed drug, which only OCCASIONALLY has serious side effects.

The correct answer is B.