Even though some of the foremost researchers of cardiovascular disease delivered a harsh critique of the guidelines due to their _______, the nongovernmental organization recommended a "heart-healthy" diet for people in countries with a low per-capita income based on data gathered mainly in affluent nations, thus failing to account for disparities in access to food.

The above highlighted are some clues to solve the blank. As these researchers are "some of the foremost researchers, " this means that they had in-depth knowledge of the topic and rarely lacked on any information. So, all the words related to this can be negated Option B is out. Although, we can imply that the researchers and the NGO were not on the same terms. And possibly the researchers failed to prove something Now, we are left with three words:

A hindsight- understanding of a situation or event only after it has happened or developed- This is not what the sentence is trying to imply- Out of Scope
C mendacity- The tendency to be untruthful- Same as A- Out of Scope
D indiscretion- behaviour or speech that is indiscreet or displays a lack of good judgement- Out of Scope
E inefficacy- Failure to produce the desire result- Fit the above pre-thinking- Correct


Hope this helps!