Exactly how does C weaken the argument? As I understand it the argument is that many economists overestimate the degree to which people are motivated by money when making job choices. The premise is that in many surveys most people do NOT name high salary as the most desirable feature of a job.
Is C implying that the reason jobs with the same salary vary in other financial benefits is because employers have to entice people to take them some how? Or is it saying that while salary may not be the most desirable feature named in most surveys, some other financial benefit may be?
In any event, it seems like an answer that just barely weakens the argument.