OFFICIAL EXPLANATION:
(Pronoun Error) The first “that” in the underlined part is a conjunction, while the second “that” (in the phrase “as that of the forty-eight states that remain”) is a singular pronoun. The earlier part of the sentence shows that there is no singular noun, which could serve as an antecedent for “as that.” So, (A) is wrong. (D) has the same error, and can be eliminated for that reason alone.
In (B), the word “worth” serves as the antecedent of the pronoun “that:” that of the forty-eight states. But this directly compares the value to the remaining states, resulting in the comparison of an apple (the worth of the cattle) and an orange (the remaining states); hence, (B) is wrong.
(C) and (E) are both grammatically correct. The difference is in the phrases “almost as much in worth as” and “worth almost as much as.” Between the two, the latter is shorter and is therefore more idiomatic, and (E) is the answer. (It is always best to choose the shorter version when in doubt; the fewer words the better, and usually the clearer.)