if we have full text of the question, it would be much easier to diagnose the question.
this is an OG question and all questions are not ideal. in gmat SC, our job is to pick the best among the available ACs, however it is always better to know why "this" and "not that".
i also agree that the use of "it" here is ambigious but A is saiid to be correct because it is the best or least worst among the 5 answer choices.
because of "them" in D and "they" in E, D/E are wrong. in B and C, it is awakward to say "awarded for", therefore they are also out. now remains A.
By a vote of 9 to 0, the Supreme Court awarded the Central Intelligence Agency broad discretionary powers enabling it to withold from the public the identities of its sources of intelligence information.
(a) enabling it to withold from the public
(b) for it to withold from the public
(c) for witholding disclosure to the public of
(d) that enable them to withold from public disclosure
(e) that they can withold public disclosure of