Dear Andy,
I'm happy to help. Yes, this is a tricky official question.

Here's the text of the question again.
In virtually any industry, technological improvements increase labor productivity, which is the output of goods and services per person-hour worked. In Parland's industries, labor productivity is significantly higher than it is in Vergia's industries. Clearly, therefore, Parland's industries must, on the whole, be further advanced technologically than Vergia's are.

The argument is most vulnerable to which of the following criticisms?
(A) It offers a conclusion that is no more than a paraphrase of one of the pieces of information provided in its support.
(B) It presents as evidence in support of a claim information that is inconsistent with other evidence presented in support of the same claim.
(C) It takes one possible cause of a condition to be the actual cause of that condition without considering any other possible causes.
(D) It takes a condition to be the effect of something that happened only after the condition already existed.
(E) It makes a distinction that presupposes the truth of the conclusion that is to be established.

First, let's think about the nature of the objection that (D) holds. Here are a series of extremely bad arguments.
Faulty argument #1: The Dred Scott decision (1857) was a direct response to the election of Abraham Lincoln (1860).
Faulty argument #2: The election of Ronald Reagan (1980) was a direct result of the fall of the Berlin Wall (1989)
Faulty argument #3: By answering your question, I caused you to ask the question.
All three of these are disastrous bad arguments, and all three make the same mistake. All three of these would be vulnerable to the objection that (D) makes. In order for X to cause Y, X must come earlier in time than Y. A cause may come immediately before an effect, or there may be a gap of minutes, hours, days, or even millions of years.
Striking a match immediately causes the match to burst into flame.
Not remembering to put gas in one's car will cause the car, a few hours or few days later, to run out of gas.
A habit of cigarette smoking, started in one's teen years, cause either cancer or heart disease over the course of decades.
The Second Amendment of the US Constitution (1789) causes American citizens today to have the gun rights they have.
The separation of N & S America from Europe & Africa, 175 million years ago, cause Columbus & the 16th century explorers to find very different animals & plants in the New World and the Old World.
The cause could happen any time before the effect, but it absolutely can't happen after the effect.

That's what (D) says.
It takes a condition to be the effect of something that happened only after the condition already existed.
In other words, the argument is interpreting a certain condition to be the effect of a particular cause, but this reputed cause took place after the condition, the supposed effect, was already happening. It's a very powerful objection to a cause-effect argument if we can demonstrate that the reputed cause took place after the effect.

Why is (D) not the OA? Well, we get no information about when any of these things happened. Time isn't discussed at all. We know Parland's industries have higher labor productivity ---that's the effect the argument is trying to explain. We have no evidence about when in time Parland started using advanced technology, or whether they use it at all. (D) would be a very power objection if a time sequence were explicitly present in the argument, but it is not.

OK, let's go back to the argument.
Parland has a higher level of labor productivity than does Vergia. This difference is what we want to explain. Why does Parland have higher labor productivity?

The argument tells us that one way to increase labor productivity is to use advanced technology. Is this the absolutely only way on earth to increase labor productivity? Absolutely not! In some cases better educated or better trained workers might be more productive, or better equipment or better supplies or better materials might help. There are many things that can contribute to labor productivity, and advanced technology is one of them.

We want to explain why Parland has higher labor productivity. It could be because Parland has more advanced technology. That could be the cause, but it doesn't have to be. The argument fallaciously assumes that advanced technology must be the cause, the only cause, of Parland's higher labor productivity.

This is another very powerful objection. If I say, "Here's a case of B. Since A causes B, A must have caused this instance of B," then a very powerful objection would be simply to point out that B has other causes besides A. Yes, we all see an instance of B, but was it caused by A or C or D? We don't know, and we can't automatically assume the one cause was responsible and not the others.

This is exactly what (C) says:
It takes one possible cause of a condition to be the actual cause of that condition without considering any other possible causes.

Part of what is hard about this is the abstract wording. Part of what is challenging, though, is that you have to have a good intuitive sense about how the business world works. Presumably you are taking the GMAT so that you can get into business school. Well, if a candidate applies to business school and then, on the interview, doesn't give any evidence of understanding how the business world works, that's not going to look good. It's very important to build your understanding of how the business world works---what factors might influence labor productivity, for example. See this blog article:
http://magoosh.com/gmat/2014/gmat-criti ... knowledge/

Does all this make sense?
Mike