Refer to Explorations in Literature for a complete version of this article.
Read this excerpt from "Nixon Resigns" by Carroll Kilpatrick:

It was exactly six years ago yesterday that the 55-year-old Californian accepted the Republican nomination for President for the second time and went on to a narrow victory in November over Democrat Hubert H. Humphrey.

Which details of this excerpt refine the central idea that Nixon's resignation is an important time in history?

A. the informal tone and the fact that these events happened six years after he accepted the party's nomination
B. the informal tone and the information about where Nixon is from
C.the formal tone and the reference to the fact that this is Nixon's second term as President of the United States
D.the formal tone and the details regarding the president's age