We are looking for the answer choice which identifies the primary purpose of both passages.
Passage A tells us that climate models are extremely complex and require a "brute force" exploration of all possible combinations of values to make predictions. We learn that current individual computers are not capable of performing such simulations; however, the simulations could be run on individual computers if they were connected to one another via the Internet.
Passage B tells us that many problems can be effectively solved using methods working in parallel simultaneously. We learn that we are currently experiencing a shift from sequential computing to massive parallel computing (i.e. using many computers simultaneously to solve one problem). The author says this new method makes sense as using a model which resembles the parallel nature of the problem it is trying to solve is likely to be successful.
In this way, both Passage A and Passage B argue that these new approaches to computing are likely to be effective ways to solve difficult problems. This is directly restated by answer choice (B), making it the correct answer.
Passage A: Public resource computing projects will help run climate simulations on individual computers
Passage B: Massive parallel computing will help solve many problems which are inherently parallel in nature.
Answer choice (D) is incorrect because neither passage suggests that their method has or should be used to solve most large-scale computing problems. Passage A is solely focused on climate modelling. Passage B tells us that many problems can be solved using massive parallel computing but this does not necessarily mean that most large-scale computing problems can be solved using this method.
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