Surveys have shown that in up to 40 percent of elderly people living i

Jayorara
True, the verb should be 'is' in A as you have said. It is an oversight. In addition, it is not clear what the word 'they' refers to. it could be 40% of the elderly people, or the elderly people, or the countries or the nutrients.

aside from pronoun ambiguity "they" in option A... is there any other reason why A is incorrect?

There are a couple of other problems with (A).

First, "up to 40 percent" is better than "in up to 40 percent". With the addition of the word "in", it sounds as though the consumption occurs within the elderly people, and that doesn't quite make sense. Choice (E) makes it clear that some portion of elderly people do the consuming. (A), on the other hand, seems to indicate that the consumption is an independent process occurring inside the elderly people... (E) is better!

Next, compare "[some elderly people] consume insufficient amounts of one or more essential nutrients" (choice E) to "the consumption of one or more essential nutrients is insufficient" (choice A). In (A), "insufficient" modifies consumption, and in (E), "insufficient" modifies amounts of one or more essential nutrients. There isn't anything inherently wrong with saying "insufficient consumption", but choice (E) makes it clear that those elderly people are not consuming a large enough quantity of those essential nutrients. So that's another small vote in favor of (E).

Last but certainly not least, the parallelism makes much more sense in (E) than in (A). In (E), it's clear that the elderly people perform two actions: they "consume insufficient amounts..." or they "have deficient levels of these nutrients." (A) is much more confusing: why use the passive structure "the consumption is... insufficient" when we could just construct the sentence with two parallel verbs?

So (E) is a much better choice. I hope this helps!

Why D is incorrect? Is it because who is modifying the countries?

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Hi porwal1, who is not modifying countries. However, clearly the position of who is not ideal, since it's quite far from elderly people.

D however, has a larger problem: D is not a complete sentence at all!

D has a structure like this:

Studies show that young people who exercise daily.

The above is clearly not a complete sentence. One way to fix it would be:

Studies show that young people who exercise daily, live healthy.

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