Originally developed for detecting air pollutants, a technique called

Hi there,

Let us split choice C into clauses:

A technique originally developed for detecting air pollutants, called proton-induced x-ray emission, which can quickly analyze the chemical elements in almost any substance without destroying it, is finding uses in medicine, archaeology, and criminology.
• A technique originally developed for detecting air pollutants, called proton-induced x-ray emission,
o which can quickly analyze the chemical elements in almost any substance without destroying it,
• (Cont. of Cl. 1) is finding uses in medicine, archaeology, and criminology.

“developed” is not a verb here. It’s a verb-ed modifier. The only verb that clause 1 has is “is finding”. (Click on the following link to learn how to distinguish between a past tense verb and verb-ed modifier: https://gmatclub.com/forum/ed-forms-verb ... l#p1100855)

In choice C, “called proton-induced x-ray emission” has been separated from the entity it should modify – “a technique”. As a result, relative pronoun “which” is now only modifying the preceding noun “proton-induced x-ray emission”. It is not modifying “a technique” anymore. This leads to the modification error in Choice C.

Same is the case with Choice D as well.

Now let’s take a look at the correct Choice A:
Originally developed for detecting air pollutants, a technique called proton-induced X-ray emission, which can quickly analyze the chemical elements in almost any substance without destroying it, is finding uses in medicine, archaeology, and criminology.

In this sentence, the opening modifier “developed” is correctly modifying the subject of the preceding clause “a technique”. Now another modifier “called…” is placed just after “a technique”. So here the sentence is really saying:
a technique = proton-induced X-ray emission
“a technique called proton-induced X-ray emission” makes one big noun phrase here and hence, “which” correctly modifies this entire noun phrase, including “a technique”.

Hope this helps.
Thanks.
Shraddha