noboru
534.
No less an authority than Walter Cronkite has reported that half of all Americans never read a book.
(A) No less an authority than
(B) Nonetheless an authority
(C) Nevertheless authoritarian
(D) Not less an authority than
(E) An authority not less than
A - is the best answer. It introduces the value of the person and is an accepted, yet somewhat awkward way to say it. (IMO)
B -
nonetheless means "in spite of" and would indicate Americans haven't read a book even though Cronkite reported on the issue
C -
authoritarian is an adjective that's completely unrelated to the sentence
D -
Not is typically used to negate something. In this case, the sentence is just using a correct, but awkward way to introduce him.
E - using "an authority" would indicate someone other than Walter Cronkite, who was at least his equal. (Since we use indefinite articles to introduce previously unreferenced nouns into conversation)
I hope that helps