Maggot therapy, the use of maggots to clear away necrotic tissue, as a method of the debridement of wounds, it was well established as early as 200 CE, but until about 40 years ago doctors did not realize that the maggots could help eliminate several different types of drug resistant bacteria.
(A) as a method of the debridement of wounds, it was well established
“Maggot therapy… as a method of the debridement of wounds” lacks a verb and thus is a fragment. Moreover, it cannot act as a modifier also because the phrase starts with noun and caanot work as an appositivr of the following subject that doesn’t exist.
(B) as a method of the debridement of wounds well established
“Maggot therapy… as a method of the debridement of wounds” lacks a verb and thus is a fragment. Moreover, it cannot act as a modifier also because the phrase starts with noun and caanot work as an appositivr of the following subject that doesn’t exist.
The whole sentence before “but” lacks a verb.
(C) was a well-established method of wound debridement
Correct choice that makes sense. “was” makes sense with “as early as”. Keep this one.
(D) was a well-established method of debriding wounds that was
“debriefing” is a gerund that is less preferred when its action noun form exists, such as “debridement”. “was” refers to “method” and implies that method was as early as.. nonsense. Method is not a time period.
(E) had been a method of wound debridement, well established
We already have “as early as” and thus past perfect is redundant. This method still continued to be useful when it was rediscovered. Hence “had been” doesn’t make sense.
Hence C