The answer choice seems to weird one, But remember we need to apply rules and eliminate choices. The sound of the sentence doesnt sound great.
A) Idiom Error: it should have said, "can hardly be said to be their fault"
B) The keyword "at fault" is not correct, it should say their fault
C) The reference of second "it" is not very clear.
D) Umm hold on
E) we're not trying to say that it is a "fact" that the educators are at fault - we're trying to say the opposite in fact - that we can't say they're at fault.
We are left with only choice, D is the answer. On the exam, there will be questions like these, but just remember your process that you have followed so far.