Butterflies come in more than 17,000 species,
displaying a wing pattern unique to each one.For this question, the best way to progress is to think about the intended meaning of the sentence before reading the answer choices. So here, the butterflies don’t really come displaying a wing pattern, right? What the sentence wants to say is that each species has a unique design/pattern.
With this in mind, let’s look at the options.
(A) displaying a wing pattern unique to each one
Here the comma + present participle modifier (verb-ing) describes the entire preceding clause/subject. If we delete the prepositional phrase and try reading the sentence, we can see that it is awkward: Butterflies come in more than 17,000 species, displaying…. It is not the butterflies but the species that come with unique patterns. Thus, we can
eliminate.
(B) displaying a unique wing pattern in each
Although the placement of ‘unique’ expresses the right intent, the modifier with a comma has the same problem as that of option A.
Eliminate.
(C) each
uniquely displaying a wing pattern
Here the meaning that comes through is erroneous. Butterflies aren’t uniquely showing or displaying patterns. Thus, we can
eliminate.
(D) each of which
displays a
unique wing pattern
This option corrects all the errors that we see in the earlier options.
This is correct.
(E) each of which
uniquely displays a wing pattern
It is not the species that is ‘uniquely displaying’ their wings; the pattern is what is unique/different.
Eliminate.
Hope this helps!