Pronoun ambiguity

[alberihem]

Question:
The invention of the cotton gin, being one of the most significant developments of the nineteenth century, had turned cotton cloth into an affordable commodity; it was costly before that.


a) being one of the most significant developments of the nineteenth century, had turned cotton cloth into an affordable commodity; it was costly before that

B) having been one of the most significant developments of the nineteenth century, turned cotton cloth into an affordable commodity, costly previously

C) one of the most significant developments of the nineteenth century, turned cotton cloth into an affordable, however costly previously, commodity

D) one of the most significant developments of the nineteenth century, turned cotton cloth into an affordable commodity, whereas it had previously been costly

E) being one of the most significant developments of the nineteenth century, turned cotton cloth from a previously costly commodity to an affordable one

The correct answer here is D).

I think "it" in answer choice D) could refer to cotton cloth or affordable commodity.

Yet, the solution claims that the pronoun "it" refers unambiguously to the "cotton cloth."

Could someone please clarify why "it" in the answer choice D) refers to cotton cloth unambiguously?

Thanks,

Albert

[tim]

The context of the sentence places the pronoun squarely within a comparison. If we are comparing the fact that "cotton cloth [turned] into an affordable commodity" with the fact that "it had previously been costly", then it is pretty clear that "it" refers to "cotton cloth". The comparison resolves any of the ambiguity that would otherwise be a problem here..