This is a tricky question overall, and "B" really contributes the most to this. There are a lot of things wrong with "B" but they are quite subtle. Let's start with employing some techniques that will help diminish the attractiveness of "B" without getting deep into its reasoning:
With weakening questions, the reasoning binding the premises and conclusions together must be attacked. Answer choice "B" doesn't do this, as it simply introduces a new fact to coincide with the current premise. That may in some instances weaken the conclusion, but it does not weaken the argument.
Arguably the first major red flag is the word "many" in the answer choice. With weakening questions, there is admittedly a particular need to respect this term, since one doesn't have to claim something like "most" in order to weaken an argument. In other words, "many" could only mean three people and could still conceivably weaken an argument even though it does virtually nothing to prove anything. Running with a mere possibility such as this should already force one to be extremely cautious, as the assumptions necessary to verify the answer choice's power to weaken are alone just about enough to move on.
Next is the issue of the preference for a high-wage job noted in "B". Thinking of this practically, of course at least some people would prefer more money over less. But does this provide any evidence for the economists' claim that financial rewards provide the STRONGEST incentive (thus weakening the argument of the author)? No. I, for one, would very much prefer a high-wage job over a lower-wage one, all else being equal. But salary is not the biggest factor for my personal job consideration.
Finally, and similarly to the last point, financial rewards are not necessarily gained wholly from wages. Benefits, bonuses, et cetera, could all fit nicely into the category of what is called financial rewards. With this in mind, "C" makes a lot of sense. Even if most people don't see a high salary as the most desirable feature of a job, these people could still consider financial rewards in general to be the biggest factor, as this could include the aforementioned benefits and bonuses, among other things.
I didn't spell this out particularly well, so I apologize in advance for the possible need for clarification (which I will be happy to give!)
Choosing the correct answer choice here depends entirely on understanding the argument in the stimulus.
The argument in the stimulus is this: Economists say that financial rewards provides the strongest incentive for people to choose one job over another. But the economists are wrong. Why are they wrong? Because surveys show that most people don't name high salary as the most desirable feature.
So you're trying to undermine the the author's argument that the economists are wrong. Does (B) undermine the argument? Well, (B) says that all else being equal, people prefer a higher paying job over a lower paying job. This should be obvious, to the point where it's borderline saying nothing.
(B) doesn't strengthen the economists' position, since it doesn't help us conclude that financial rewards are the *strongest* incentive. The economists are comparing financial rewards to other aspects of a job, such as location, hours, etc. By contrast, (B) is comparing salary of one job to salary of another job, all else (location, hours, etc.) being equal.
(B) also doesn't weaken the author's argument that the economists are wrong. People preferring a higher paying job to a lower paying job is entirely consistent with high salary not being the most desirable feature. Again, the surveys the author is discussing are comparing salary vs. other aspects (location, hours, etc.), while (B) is comparing high salary vs. low salary.
(C) does weaken the author's argument, but it's a very weak weakening. (C) says that jobs with the same salary can vary considerably in their other financial benefits (bonuses, insurance, retirement, etc.). So this sneaks in the possibility that, although high salary isn't the most desirable feature of a job, maybe good insurance and high bonuses are the most desirable features. If this is true, then the economists are still right -- financial rewards *are* the strongest incentive for choosing one job over another. The key is to realize that "high salary" is only a subset of "financial rewards", and that other things like bonuses are also part of financial rewards. (C) exploits this fact.
Let's break this down into the premises and the conclusion: Premise : In surveys people don't name high salary as the most important feature of a job Conclusion: Economists overestimate how important money is when choosing a job (they claim financial rewards are THE STONGEST incentive for choosing a job). So the conclusion is that money/financial rewards are not THE STRONGEST incentive for choosing a job.
At a first glance, it looks OK: people say that salary is not the most important in choosing a job, and that appears to support the conclusion that to most people money is not the most important thing in choosing a job. We need to find an answer that weakens the connection between the premise and the conclusion. Right off the bat, we can see that there's a subtle shift between the wording of the premise and the conclusion. The premise mentions that salary is not the most important, and the conclusion says that financial rewards are not the most important. The correct answer will probably exploit this.
Answer C (correct) does exactly that. It points out that you can have the same salary, but very different total compensation. Job A (CEO of Apple) pays a 1$ salary, but offers close to $100 million in stock options/shares. Job B (janitor at a public school) pays $20,000 salary and offers nothing else in terms of financial compensation.
So, I can be totally motivated by money and nothing else, and still honestly say that salary is not my most important consideration in choosing job A over job B.
Answer B doesn't weaken because if you take away any other possible differences between two jobs, money has to be the most important consideration - there's nothing else to consider! So it's not a fair comparison to the original argument.
Comments
With weakening questions, the reasoning binding the premises and conclusions together must be attacked. Answer choice "B" doesn't do this, as it simply introduces a new fact to coincide with the current premise. That may in some instances weaken the conclusion, but it does not weaken the argument.
Arguably the first major red flag is the word "many" in the answer choice. With weakening questions, there is admittedly a particular need to respect this term, since one doesn't have to claim something like "most" in order to weaken an argument. In other words, "many" could only mean three people and could still conceivably weaken an argument even though it does virtually nothing to prove anything. Running with a mere possibility such as this should already force one to be extremely cautious, as the assumptions necessary to verify the answer choice's power to weaken are alone just about enough to move on.
Next is the issue of the preference for a high-wage job noted in "B". Thinking of this practically, of course at least some people would prefer more money over less. But does this provide any evidence for the economists' claim that financial rewards provide the STRONGEST incentive (thus weakening the argument of the author)? No. I, for one, would very much prefer a high-wage job over a lower-wage one, all else being equal. But salary is not the biggest factor for my personal job consideration.
Finally, and similarly to the last point, financial rewards are not necessarily gained wholly from wages. Benefits, bonuses, et cetera, could all fit nicely into the category of what is called financial rewards. With this in mind, "C" makes a lot of sense. Even if most people don't see a high salary as the most desirable feature of a job, these people could still consider financial rewards in general to be the biggest factor, as this could include the aforementioned benefits and bonuses, among other things.
I didn't spell this out particularly well, so I apologize in advance for the possible need for clarification (which I will be happy to give!)
The argument in the stimulus is this: Economists say that financial rewards provides the strongest incentive for people to choose one job over another. But the economists are wrong. Why are they wrong? Because surveys show that most people don't name high salary as the most desirable feature.
So you're trying to undermine the the author's argument that the economists are wrong. Does (B) undermine the argument? Well, (B) says that all else being equal, people prefer a higher paying job over a lower paying job. This should be obvious, to the point where it's borderline saying nothing.
(B) doesn't strengthen the economists' position, since it doesn't help us conclude that financial rewards are the *strongest* incentive. The economists are comparing financial rewards to other aspects of a job, such as location, hours, etc. By contrast, (B) is comparing salary of one job to salary of another job, all else (location, hours, etc.) being equal.
(B) also doesn't weaken the author's argument that the economists are wrong. People preferring a higher paying job to a lower paying job is entirely consistent with high salary not being the most desirable feature. Again, the surveys the author is discussing are comparing salary vs. other aspects (location, hours, etc.), while (B) is comparing high salary vs. low salary.
(C) does weaken the author's argument, but it's a very weak weakening. (C) says that jobs with the same salary can vary considerably in their other financial benefits (bonuses, insurance, retirement, etc.). So this sneaks in the possibility that, although high salary isn't the most desirable feature of a job, maybe good insurance and high bonuses are the most desirable features. If this is true, then the economists are still right -- financial rewards *are* the strongest incentive for choosing one job over another. The key is to realize that "high salary" is only a subset of "financial rewards", and that other things like bonuses are also part of financial rewards. (C) exploits this fact.
Premise : In surveys people don't name high salary as the most important feature of a job
Conclusion: Economists overestimate how important money is when choosing a job (they claim financial rewards are THE STONGEST incentive for choosing a job). So the conclusion is that money/financial rewards are not THE STRONGEST incentive for choosing a job.
At a first glance, it looks OK: people say that salary is not the most important in choosing a job, and that appears to support the conclusion that to most people money is not the most important thing in choosing a job.
We need to find an answer that weakens the connection between the premise and the conclusion.
Right off the bat, we can see that there's a subtle shift between the wording of the premise and the conclusion. The premise mentions that salary is not the most important, and the conclusion says that financial rewards are not the most important. The correct answer will probably exploit this.
Answer C (correct) does exactly that. It points out that you can have the same salary, but very different total compensation.
Job A (CEO of Apple) pays a 1$ salary, but offers close to $100 million in stock options/shares.
Job B (janitor at a public school) pays $20,000 salary and offers nothing else in terms of financial compensation.
So, I can be totally motivated by money and nothing else, and still honestly say that salary is not my most important consideration in choosing job A over job B.
Answer B doesn't weaken because if you take away any other possible differences between two jobs, money has to be the most important consideration - there's nothing else to consider! So it's not a fair comparison to the original argument.