I’m happy to help. In order to understand why B is not the answer that most seriously weakens the argument, let’s first take a look at the argument itself.
We learn from the passage that of people surveyed who sought a psychologist’s help, of those who received treatment for 6 months or less, 20 percent claimed it made things better. Of those who received treatment for longer, 36 percent claimed it made things better. And then we get a conclusion: longer treatment is more effective.
Answer B says: patients who received longer treatment were more likely to respond.
Why would that weaken the conclusion? All that an increase in response volume means is that the latter group gets a bigger sample size than we otherwise knew. But a larger volume has no impact (that we know of) on the rate of claiming that psychological help made things better. And therefore this assumption does not weaken the argument that longer treatment is more effective.
Instead, consider answer C. For this answer, we are told that patients who feel they are doing well tend to remain in treatment. This would weaken the conclusion that 6 months is more effective than shorter term treatment, because it tells us that our samples are skewed — the group that stays past 6 months feel they are doing well, and felt that way even before the six month mark!
I hope that helps. Please let us know if you have further questions.
Ilma August 14, 2020
but B also weakens the argument by saying that "patients who recieved longer treatment were more likely to respond" since, if most people from the <6 months group did not even participate in the survey then how can the author conclude on the basis of that survey that >6 months, i.e., longer treatment is more effective. Maybe it was just the fact that since more people participated from the >6 months group therefore there were more people from that group who claimed "it made things better"
This options attacks the very basis on which the conclusion stands so doesn't it weaken the conc.?
