You are given a background paragraph that describes one or more causal or qualitative relationships such as a relationship in economics or a scientific law and a story that makes use of the concepts or the relationship described in the provided paragraph. You are also given a question about the story that requires an understanding of the relationship described in the background paragraph and the story. You need to come up with an answer to the given question; the answer will be a span from either the question or the story. In order to correctly answer the given question, you need to understand the relationship mentioned in the background paragraph and should be able to use it to understand that in the story. Your answer can not consist of any word that is not mentioned in any of these: the background paragraph, the story, or the question. You can directly copy and paste a span from the story or the question while answering the given question.

[EX Q]: Background Paragraph: A wood-decay fungus is any species of fungus that digests moist wood, causing it to rot. Some species of wood-decay fungi attack dead wood, such as brown rot, and some, such as Armillaria (honey fungus), are parasitic and colonize living trees. Excessive moisture above the fibre saturation point in wood is required for fungal colonization and proliferation.[1] Fungi that not only grow on wood but permeate its fibrous structure and actually cause decay, are called lignicolous fungi. In nature, this process causes the breakdown of complex molecules and leads to the return of nutrients to the soil.[2] Various lignicolous fungi consume wood in various ways; for example, some attack the carbohydrates in wood and some others decay lignin. The rate of decay of wooden materials in various climates can be estimated by empirical models.[3]. 
Story: Bob is a botanist. His interest is in different kinds of fungi. He went to Brazil last month to study fungi in 
the Amazon rain forest. First day he searched for fungi in a location with excessive moisture. Second day he searched for fungi in a location with no moisture. In all his search he found two specimens of fungi. Specimen A is a brown rot fungus, and specimen B is a honey fungus. 
Question: Would specimen A fungus live on dead woods or not live on dead woods?
[EX A]: live on dead woods.

[EX Q]: Background Paragraph: The ionization energies of the representative elements generally decrease from top to bottom within a group. This trend is explained by the increase in size of the atoms within a group. The valence electron that is being removed is further from the nucleus in the case of a larger atom. The attractive force between the valence electron and the nucleus weakens as the distance between them increases and as the shielding effect increases, resulting in a lower ionization energy for the larger atoms within a group. Although the nucl. 
Story: Rob is learning about ionization. He looks at a specific group of elements from top to bottom to figure out thier ionization energy. 
Question: Which element will have a higher shielding effect, the top element or the bottom element?
[EX A]: bottom element.

[EX Q]: Background Paragraph: In Windows 2000 and later the threads in the System Idle Process are also used to implement CPU power saving. The exact power saving scheme depends on the operating system version and on the hardware and firmware capabilities of the system in question. For instance, on x86 processors under Windows 2000, the idle thread will run a loop of halt instructions, which causes the CPU to turn off many internal components until an interrupt request arrives. Later versions of Windows implement more complex CPU power saving methods. On these systems the idle thread will call routines in the Hardware Abstraction Layer to reduce CPU clock speed or to implement other power-saving mechanisms. 
Story: Bob is building a new computer and wants it to be the most advanced version he can make. He has all of his parts, but is not deciding on a operating system. He sees that Windows 2000 is on sale, but also isn't sure if it will do what he wants, and has the choice to pay a higher price for Windows 10. His other goal is to make sure that his machine is efficient, and won't cost a lot in the way of power costs while running, since he leaves his machine idle most days. 
Question: Which operating system should Bob buy if he wants the best power efficiency?
[EX A]:
Windows 10.