174. 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

In this sentence, the relative pronoun that should introduce the clause The Adventures ... published to make a relative clause modifying year. Also, the singular title of the novel demands a singular verb: for example, one would say, "The Adventures of Huckleberry Finn is (not "are") a great book." Only C, the best choice, satisfies both requirements. Choices A and D incorrectly substitute as for that to introduce the relative clause. Choice A also mistakes the novel title for a plural (were published). B confuses meaning (written in the same year of publication as). E creates a similar confusion of meaning, and both D and E are awkward and imprecise because that is too far away from its referent (letter) to be clear 解释中说The Adventures ... published to make a relative clause modifying year，那么that也就是修饰year的，可是这个看上去不像一个定语从句啊!定语从句的先行词一般都可以放回定语从句中，可是year并不能放回去啊!?难道是同位语从句？

我想问的是关于due to的省略问题.请问下面哪些话是对的:

Our declining health is more due to the polluted air than due to  the polluted water. 

Our declining health is more due to the polluted air than to the polluted water.                                             省略due

Our declining health is more due to the polluted air than the polluted water.                                                  省略due to