I believe that the answer is A, to emphasize a point.
The correct answer is the last one. Kilpatrick's article shares how White House staff feels about Nixon's resignation.
In the article, numerous aides and officials are quoted. Each gives his thoughts and/or opinions on Nixon's resignation. Many are sorry to see him go. Therefore the second option -- that the staff is unaffected -- is not correct.
The article does not say much about who will become president after Nixon. Furthermore, the staff itself is not changing; only Nixon is leaving. Therefore, the final answer is the correct one.
D. — perfect future.
The reasoning being that perfect future is a verb tense that is used when there’s an action that will be completed in the future.
Hope this helps. ^^
