Explanation

Reading the question: we can begin once again with the question stem, as we did for Drivers Over 30. We don't have to start with the stem on every question, but if it feels counterintuitive to start with the stem first, let's exercise that muscle.

Creating a filter: the stem tells us to choose something that is "useful" to evaluate the argument. Quite often, as we'll discuss more on later questions, the correct answer will be not only "useful," but essential to the argument. (This is proof by stronger terms, as mentioned in the Critical Reasoning Strategy.) What's essential to the argument? The language of the argument gets passionate with the phrase "immediately speed understanding." Working back from that phrase, what immediately speeds understanding? The green pig technology makes traceable cells and we are going to transplant those into a human. That's the key connection: 1) the traceable cells and 2) the immediate speeding of understanding. With that connection mind, we can now turn to the answer choices. We'll see, for starters, what answer choices have anything to do with 1) the traceable cells and 2) the immediate speeding of understanding. Since we are "filtering" out the irrelevant answer choices, we can think of this as a basic relevance filter.

Applying the filter: Choice (A) doesn't pass the filter. Choice (B) is definitely irrelevant to the argument. Skipping down, so is (E). They have no bearing on how the green piggery will help genetic research. Choices (C) and (D), interestingly, both involve time, which pertains to the word "immediately" in the prompt.

Logical proof: we can analyze both (C) and (D) by extreme cases; this is step 2 of the Critical Reasoning Strategy presented at the beginning of the book. First, (C). We imagine the technique takes a long time to be perfected--or it's never perfected. That might not matter, if the new technique is already a big improvement. So we're focused on (D). Choice (D) says, if the current pig process churns out completely green pigs only occasionally, we can't benefit much from them. Maybe the new process is much better, but not that good. That would be highly relevant to the argument. The correct answer is (D).