In OG, the answer is B). And the explanation it gave regarding choice E) is
"The second boldfaced portion is not offered as support for the conclusion; if it were offered as such support, the argument would be guilty of circular reasoning, since the second portion states exactly what the argument concludes"
I tend to agree with this explanation. Notice that The 2nd part ( i.e. the boldface ) is NOT the question it is posing. It is just the statement that Delta is consuming less fossil fuel than it did before, which is the conclusion itself.
I agree that the wording is confusing. Regardless, the takeaway for me is that in answering the boldfaced questions, one needs to be careful in picking what the conclusion is first.