Premise 1: Program says choose careers which require college degrees
Premise 2: Increase in % of high school grads entering college
Conclusion: Program successful.
Pre-thinking1. High school grads in with the objective of choosing careers requiring college degrees
2. No other factors such as lower fee, easing admission requirements, etc.
(A) The number of graduates who went on to college remained constant each year during the 10-year period.
Incorrect. The argument is about percentage and accordingly the number can be constant or decrease or increase. Since we're concerned about the proportion of high school graduates entering college.
(B) Any college courses that the graduates take will improve their career prospects.
Incorrect. This is just repeating the premise. Not a missing premise or a logical gap that the assumption answer would be expected to fill.
(C) Some of the graduates who went on to college never received guidance from a high school counselor.
Incorrect. This is a weakener. If some of the graduates never received guidance from HS counselor, the program cannot be said to be successful. Alternatively, negative this and this would actually strengthen the conclusion.
(D) There has been a decrease in the number of graduates who go on to college without career plans.
Incorrect. If you negate this, you get "there has not been a decrease in the no. of grads who go on to college w/o career plans". Now this doesn't necessarily destroy the conclusion. It could simply be possible that the number of grads coming with the purpose of getting into careers which require a college degree has increased sharply.
(E) Many of last year's graduates who went on to college did so in order to prepare for careers requiring college degrees.
Correct answer. Negate this and we get "Many of last year's grads... for careers not requiring college degrees" This absolutely destroys the conclusion in so far as we now know that most college goers are not there with the intent that is preached by the programme. Therefore, the programme has not worked. Correct answer.