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A. satellites that is a part of 15 years effort of subjecting the interactions of Earth's atmosphere, oceans, and land surfaces
There are a couple of small problems with (A). First, we have a subject-verb agreement issue at the beginning of the underlined portion, but it’s a little bit tricky: “the AM-1 is one of the many new satellites that is part of 15 years effort…” You could argue that the phrase “that is part” modifies the singular noun “
one of the many new satellites”, but I don’t think that’s quite right: ALL of the satellites ARE part of the effort, so we need a plural verb.
And then we have some minor idiom issues. For starters, the phrase “15 years effort” isn’t quite right. I guess it would be better if “years” was possessive, but even then, it’s odd. And it would make much more sense to call it a “15-year effort.”
Plus, it also makes more sense to say “an effort
to subject the interactions… to scrutiny”, not “an effort of subjecting…”
So we have lots of reasons to ditch (A).
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B. satellites, which is a part of a 15-year effort to subject how Earth's atmosphere, oceans, and land surfaces interact
(B) has a similar subject-verb agreement problem as (A): “…one of the many satellites, which
is part of…” Again, that doesn’t make much sense, since ALL of the satellites are part of the effort, so we need a plural verb.
And this is a very minor thing, but I don’t love the use of “which” here in general. Modifiers beginning with “which” are non-essential modifiers, meaning that the modifier isn’t strictly necessary for us to grasp the meaning of the sentence. But I think we DO need the modifier (“that are part of a 15-year effort…”) in order to understand exactly which satellites we’re talking about.
I don’t think that the difference between “which” (non-essential modifier) and “that” (essential modifier) has ever been the deciding factor on an official SC question, but it gives us an extra reason to get rid of (B).
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C. satellites, part of 15 years effort of subjecting how Earth's atmosphere, oceans, and land surfaces are interacting
As in (B), there’s a subtle problem with a non-essential modifier: “…one of the many new satellites, part of 15 years effort…” That’s not WRONG, exactly, but it turns the description of the satellites into an incidental, non-essential modifier. It makes more sense to say “… one of the many new satellites THAT are part of a 15-year effort…”
And just like in (A), we have that goofy little phrases “15 years effort” and “effort of subjecting.” See the explanation of (A) for more on these two issues.
Finally, there’s no good reason for the verb tense at the end of the underlined portion: “are interacting” (present progressive tense, if you’re a fan of grammar jargon) emphasizes the fact that the interactions are happening right now, and there’s no real reason to do that. As we’ll see in a moment, there are more elegant ways to phrase this without using an unnecessarily complex verb tense.
So (C) is out.
Let’s line up the last two side-by-side to make it easier to see the differences:
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D. satellites that are part of an effort for 15 years that has subjected the interactions of Earth's atmosphere, oceans, and land surfaces
E. satellites that are part of a 15-year effort to subject the interactions of Earth's atmosphere, ocean, and land surfaces
There aren’t tons of differences between these last two. In (D), we have “an effort for 15 years”, and that’s nowhere near as elegant as the phrase used in (E), “a 15-year effort.” That’s not a dealbreaker, but it gives us a small reason to prefer (E).
But the other issue is the way the end of the underlined portion is phrased. Let’s strip these down a bit:
(D) “… an effort… that has subjected the interactions… to scrutiny from space.”
(E) “… an effort… to subject the interactions… to scrutiny from space.”
I think we’d all agree that (E) is more clear and succinct than (D) in this part of the sentence. It’s not that (D) is necessarily WRONG, but we have two decent reasons to think that (E) is better than (D). So (E) is our answer.