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So the items we have are:
1: fluctuations IN local seismic activity
2: tilting [and blah blah blah] OF the Earth’s crust
3: changing the measured strain ACROSS……[wait a minute! "changing" is used as a VERB here, this is not consistent with "fluctuations" and "tilting" which were used as NOUNS above.
4: varying the electrical properties [AGAIN, "varying" is used as a VERB]

So what we need is the NOUN from of the word “changing” followed by some kind of prepositional word like “IN” or “ON” or “OF”

So going down the answer choices, we see in (B), “changing” is used as an adjective. In (C), “changing” is used as a verb. Only in (D) and (E) we see “changes”–a NOUN, that’s what we want. They are both followed by a prepositional phrase “IN”—”changes IN blah blah blah”

Comparing (D) and (E), (E) seems extra wordy. (D) says the same thing in less words. Notice I do not clearly know what the correct idiom is: “variations in” or “variations among”–but that DOES NOT MATTER.

Hope that helps.

Zeke

Zeke Lee wrote:
xxxxxxx,
Your reasoning is correct. However, notice the word “providing” is underlined in the original sentence.

If you choose answer choice B, you are no longer talking about “the act of providing costs.” The sentence would read: “officials are quick to point out that healthcare benefits costs…”—which does not make sense. It should be “cost” in this case, not “costs.”

Be careful which words are underlined. Hope that helps.

Zeke

Just going through your explanations for this question, you say that “The act of providing” is Singular and we need to have “costs” , But why do we choose D ?
Please explain.

Thanks
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