College graduates = A, authoritative = B, resourceful = C.
According to the premises, (A -> B | C), and (only ~B -> ~C), which equals B -> C and ~C -> ~B (remember the NOT Triangle – when you apply two of the three operations on a statement, the meaning stays the same).
The conclusion states (impossible for A -> B), which equals (A -> ~B).
“Only people who lack authoritativeness lack resourcefulness” does not mean all people who lack authoritativeness lack resourcefulness. Only that, if you are not resourceful, you must also not be authoritative.
You know from the first premise that college graduates can be either authoritative or resourceful, which means they cannot be both and cannot be neither. If this was the only premise, then the conclusion would not follow. However, you know from the second premise that only people (of which college graduates are a subgroup) who are not authoritative can also not be resourceful, which means anybody who is authoritative must also be resourceful. Since this would contradict the first premise, it is impossible.
In other words:
The only possible scenario that would not contradict the combination of the premises is a scenario in which all college graduates are only resourceful. Therefore, the conclusion follows.
The correct answer is A