Here's the
official explanation provided by the GMAC for this question:
This sentence reports an effect (universities turning to a new source of funding) resulting from two changes. Each of the changes is stated in terms of what is
no longer happening, and the opening word
with encompasses both of the
no longer phrases. Answer choices C, D, and E all contain inept, unidiomatic wording. The wording in answer choice B differs from the original version only in using
had where the original uses
did.
Did functions here as a pro-verb representing the verb
carry.
No longer able to carry the burden it once had makes sense, but it is a little odd. It implies that private philanthropy no longer has this burden. If it no longer has the burden, whether it can still carry it is irrelevant. To have a burden and to carry a burden typically do not mean quite the same thing.
The burden it once had suggests that private philanthropy was burdened by the funding in the way that a person might be burdened.
Option A: Correct. This straightforwardly expresses a coherent meaning using standard forms of expression and appropriate verb forms. The two
no longer constructions are appropriately parallel.
Option B: The problem with this version is subtle.
The burden it once had implies that private philanthropy no longer has this burden. If it no longer has the burden, whether it can still carry it is irrelevant. To have a burden and to carry a burden typically do not mean quite the same thing.
The burden it once had suggests that private philanthropy was burdened by the funding in the way that a person might be burdened.
Option C: This has the same subtle problem as answer choice B. Also,
the burden which it had once is awkward and nonstandard. Placing
once after the verb suggests that the author intends to say that it had the burden one single time, rather than that it used to have the burden. The word
which is unnecessary.
Option D: Having the ability of carrying is awkward, verbose, and unidiomatic. Furthermore, this has the same subtle problem as answer choice B.
Option E: This is very awkward, wordy, and indirect.
No longer with the ability of carrying is unidiomatic and unclear. Placing
once after the verb suggests that the author intends to say that it carried the burden one single time, rather than that it used to carry the burden.
The correct answer is A.
Please note that I'm not the author of this explanation. I'm just posting it here since I believe it can help the community.