Bunuel
Nearly all employees of the factory who have completed their high school diploma have earned their factory safety certificate, having easily completed the eight week training course. The high school graduates who haven't earned the certificate are ones who have evening obligations that have prevented them from taking the course. Overall, though, most of the factory workers have not earned the certificate.
If the statements above are true, which one of the following also must be true?
A. A large proportion of students with high school diplomas have evening obligations that have prevented them from taking the eight week training course.
B. No factory worker without a high school diploma has completed the course and earned the certificate.
C. Most of the workers who have earned the certificate are high school graduates.
D. A large proportion of the factory workers have not graduated from high school.
E. Most of the people who take the training course are able to earn the safety certificate.
OFFICIAL EXPLANATION
The credited answer is (D). If most factory workers with high school degrees have completed the training, then most of the factory workers who haven't completed the training must be folks without high school degrees. Since the factory workers who haven't completed the training in the vast majority, and since factory workers with high school degrees can only account for a very small number of these, then most of the factory workers must not have high school degrees.
We don't know how many factory workers with high school degrees have evening obligations. We know that the factory workers with high school degrees who haven't completed the training have evening obligations that prevent them from completing it, but among the factory workers with high school degrees who have completed the training, we don't know what proportion has evening obligations, and how the size of this group might compare to the number of the factory workers with high school degrees who haven't completed the training. Choice (A) is incorrect.
As explained above, the information lead us to deduce that many factory workers without high school degrees haven't completed the training course, but that does mean that none have. Choice (B) is too extreme, and it is incorrect.
We don't know the relative proportions of worker with or without high school degrees; as discuss above, we have grounds to suspect that the latter is a larger group. We know that many of the factory workers with high school degrees have completed the training and have earned the certificate, but we have no idea what proportion of the factory workers without high school degrees have done so, and how the number of this latter group compares to the former group. We have no way to know which is greater. Choice (C) is incorrect.
The information suggests that, among high school graduates, most of the folks who took the course were able to earn the certificate with little difficulty. Is this generally the case? Is it the case for folks who weren't able, for whatever reason, to complete their high school degree? We don't know. The prompt provides no information on this point. Choice (E) is incorrect.