A letter by Mark Twain, written in the same year as The Adventures of Huckleberry Finn were published,
reveals that Twain provided financial assistance to one of the first Black students at Yale Law School.
(A) A letter by Mark Twain, written in the same year as The Adventures of Huckleberry Finn were
published,
(B) A letter by Mark Twain, written in the same year of publication as The Adventures of Huckleberry Finn,
(C) A letter by Mark Twain, written in the same year that The Adventures of Huckleberry Finn was
published,
(D) Mark Twain wrote a letter in the same year as he published The Adventures of Huckleberry Finn that
(E) Mark Twain wrote a letter in the same year of publication as The Adventures of Huckleberry Finn that

Can anyone pls explain wht the ans is C. I am confused between B and C. I understand about singular subject and plural verb but not about relative pronoun part as explained in OG.

Thanks for all help.