Explanation

In our initial approach, a prediction of the answer may not spring to mind. Here we can make use of the fact that, on questions asking for an assumption, the answer choices can always be evaluated with the negation test or analysis by cases. If we apply the test correctly, we won't need a filter.

Logical proof: If (A) is negated, the conclusion is truer, if anything. So (A) is out. We'll negate (B); even if employees leak information sometimes, if it's shared progressively less as it propagates outward, the argument is still true, because the leak was either on the outside and there was less info to leak, or it leaked near the center but got muffled on the way to the outside. So (B) is out. We negate (C); if CEOs were unwilling to distort information, that wouldn't hurt the argument, because the information could still be "shielded"; (C) is not very relevant. (C) is out. We like (D), we skip forward and swiftly call (E) irrelevant. Back to (D), our favorite. We'll negate it: if the public obtains information from outside the company--maybe lots of information or superior information, even--then the public doesn't necessary have less negative information. (D) is evidently a critical assumption. The correct answer is (D).