This is a very interesting question. One of the easiest splits among the answer choices to spot is that each choice has a different verb, "is"/"is going to be"/"will cost" etc. Verb tense isn't my favorite place to start, because the rules for tense admit so many exceptions, but the other differences among the answer choices don't offer any firmer ground, so let's start here.
Consider the structure
As X, Y, where
X and
Y represent noun clauses, and "as" means "at the same time as." Here are two examples:
Example 1 As Academy members and invited guests leave their seats, they will be replaced by hired seat-fillers.
Example 2 As Academy members and invited guests leave their seats, they are replaced by hired seat-fillers.
Each of these is correct for a different circumstance.
Example 1, which uses simple present tense in the X portion and a simple future tense in the Y portion is the more common. It shows the combination of tenses appropriate for writing about a specific future action or event, say next year's Oscar ceremony.
Example 2, which uses simple present tense in both portions is appropriate for writing about a general rule, say the a rule for all Oscar ceremonies.
Example 1 is appropriate here. So eliminate answers A and B. I won't say much about E here, since it has no partisans, so let's focus on C and D. One problem with C is that the phrase "well over an extra 50 basis points per year" seems to be an appositive, and so more or less synonymous with the phrase "interest rates." This is wrong, the interest rates are not "well over an extra 50 basis points a year", the
increase in the interest rates is "well over an extra 50 basis points a year." That leaves D.
I think that D sounds horrible, by the way, but if this were an actual GMAT questions, I'd choose D even so.