Can someone explain this ?
Since, I do not know what answer choices are available as option here, I will go ahead and try to to explain it as a TC question.
As you can see the term ‘although’ , is setting up a contrast in the two segments of the given statement, so since the blank is in the first part, we will look at the second segment of the statement to find out which idea is to be contrasted.
The second statement says “increasing local allegation of preferential treatment are threatening…”, the term "preferential suggest that allegations say that system is biased.
so we will have to look for a contrast of this idea in the first segment
The first segment says “the system’s ----- is not currently in dispute”, which suggests (due to contrast) that the system is viewed as unbiased currently , so the answer would be a word of phrase supporting that idea(that currently the system is unbiased , but allegations of being biased is threatening to change this view).