Good questions! The first thing to focus on here is the question task. It is an assumption question. This means that we are instructed to find a necessary but unstated belief the author must have in order for her conclusion to be valid.
Let's focus on the conclusion. The author concludes that the current efficiencies in use will lead to even greater savings in the future.
Now let's assess the evidence. To back up this conclusion, the author cites current savings that these efficiencies have created.
Pause for a moment to describe what's right and wrong about this argument. First of all, is the current evidence sound and relevant? In other words, do we have good reasons to believe these efficiencies create savings? It certainly seems that way. The first couple statements in the stimulus provide ample evidence that these efficiencies have created savings in the present day.
Now let's move to the next logical step: using the evidence provided, can we get from where we are right not—several billion dollars in savings—to where the author tells us we're going to go—$200 billion in savings in 50 to 100 years?
Where's the evidence? I don't see much good evidence to back up this point. How do we know for sure this stuff is going to continue to work in the future? How did we come up with this $200 billion figure?
That's where the issue is.
We are asked what one of the author's assumptions is. Let's remind ourselves what we noticed wrong with this argument:
- How do we know for sure this stuff is going to continue to work in the future?
- How did we come up with this $200 billion figure?
What would the author have to believe in order for this argument to make sense? The author must believe that:
- These efficiencies are going to continue to be great cost savers for the next 50 to 100 years.
- These efficiencies are going to be so super that we're going to ramp up the savings all the way too a cool $200 billion.
What do we need in an answer choice? We need an answer that will describe one of these essential beliefs the author has.
This is the definition of an assumption task.
(A) This is the credited answer choice.
The author must believe these technologies are going to continue to be available and cost effective for the next 50 to 100 years. Why must the author believe this? Do the Assumption Negation Test™. What if these technologies all became too expensive to use over the next 50 to 100 years. Would we be saving money then? No. The savings wouldn't work out, certainly not up to $200 billion. Therefore, this is an essential belief of the author, a necessary assumption, and the correct answer.
(B) This answer is irrelevant. Maybe a crisis happens. Maybe one doesn't. Either way, the author doesn't have to believe anything about oil crises for her argument to work.
(C) What if buildings become less important? What if they do? Either way, our argument is unaffected or only marginally affected.
(D) This answer gives a precise figure in the amount of the energy bills in the future. There's that $200 billion number! This is a trap answer. The information in this answer would certainly strengthen the conclusion! If we knew for sure that bills would be $200 billion less in the future, I'd feel comfortable saying that backs up our claim that these technologies will be helpful in the future. However, do we have to believe that energy bills are going to be lower by this $200 billion amount? No we do not. The author only concludes that the efficiencies will lead to $200 billion in savings. The bills might be considerably higher, but they could still be $200 billion less than what they would have been without these efficiencies. Therefore, this answer is not an assumption but only a hypothetical helpful statement.
(E) You got this one right in noting that new technologies do not come up in the stimulus. That's not our concern here. We're only interested in the savings generated by the current efficiencies, nothing else. Therefore this is irrelevant.
Good job with your analysis. I hope this helps!