An item on PSAT 1:
They know it as colony collapse disorder (CCD), this phenomenon will have a detrimental impact on global agriculture if its causes and solutions are not determined.
A) NO CHANGE
B) Known as colony
C) It is known as colony
Choice A is wrong because it’s a comma splice.
Choice B is correct.
Choice C is wrong because it’s a comma splice, too.
Why is Choice D wrong?
I think it’s wrong because “colony” is a noun that lacks a noun “slot” (or function) in the sentence: it’s not a subject; it’s not an object; it’s not a complement. It’s nothing, really. At least, it’s nothing in terms of the sentence.
Is there a different way to see it?