Official Explanation
by TommyWallach
No two quarries are alike, and it requires a degree of study to interpret what went on in the past.
(A) No two quarries are alike, and it requires
PROBLEM: I want to make very clear that the issue here is NOT a pronoun issue. You're allowed to use "it" like this, with no antecedent, at the beginning of clauses. For example, "It is really hot out today." The problem is more that the logic of the sentence is totally unclear. If we don't refer to the quarries in the second half of the sentence, it becomes unclear what exactly we're trying to "interpret" about "the past."
(B) Two quarries are not alike, and either requires
PROBLEM: "Two quarries are not alike" changes the meaning, making it sound like there are just two quarries we're discussing, instead of making a general point. Using "either" makes it sound like there are only two quarries, when instead we're trying to make a general point about quarries.
(C) Neither two quarries are alike, and each requires
PROBLEM: "Neither two quarries are alike" is gibberish.
(D) No two quarries are alike, and each requires
ANSWER: "Each" is an adjective/pronoun that is used to refer to each of two or more things INDIVIDUALLY. Though "each" itself is singular, we OFTEN use it to refer to plural nouns. "Each of my uncles is crazy." Think of it having an understood "one" after it whenever its used on its own.
(E) No two quarries are alike, and either requires
PROBLEM: Using "either" makes it sound like there are only two quarries, when instead we're trying to make a general point about quarries.
Hope that helps!