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: Predators play an important role in an ecosystem. For example, if they did not exist, then a single species could become dominant over others. Grazers on a grassland keep grass from growing out of control. Predators can be keystone species . These are species that can have a large effect on the balance of organisms in an ecosystem. For example, if all of the wolves are removed from a population, then the population of deer or rabbits may increase. If there are too many deer, then they may decrease the amount of plants or grasses in the ecosystem. Decreased levels of producers may then have a detrimental effect on the whole ecosystem. In this example, the wolves would be a keystone species. 
Story: Two students studied animal behavior for the biology class. Ned studied more about predators, while Kim studied more about herbivores. 
Question: Which student learned less about deer?
[EX A]: Ned.

[EX Q]: Background Paragraph: In a bakery, angel food cakes could be baked in a rack oven, revolving oven, convention oven, or small deck oven. A commercial bakery may use a tunnel or traveling oven.[7] When the cake has finished baking, it should have a golden brown color on the exposed area.[5] The final volume will generally be two to three times larger than the batter volume.[6]. 
Story: Two bakeries were famous in town for their angel food cakes. Tom's was a small bakery with various small ovens, took small orders and did some catering. Bill's bakery was large and produced angel food cake commercially, in vast quantities. 
Question: Which bakery used a tunnel oven to bake angel food cakes?
[EX A]: Bill's.

[EX Q]: Background Paragraph: Since AM fungi are biotrophic, they are dependent on plants for the growth of their hyphal networks. Growing a cover crop extends the time for AM growth into the autumn, winter, and spring. Promotion of hyphal growth creates a more extensive hyphal network. The mycorrhizal colonization increase found in cover crops systems may be largely attributed to an increase in the extraradical hyphal network that can colonize the roots of the new crop (Boswell et al. 1998). The extraradical mycelia are able to survive the winter, providing rapid spring colonization and early season symbiosis (McGonigle and Miller 1999). This early symbiosis allows plants to tap into the well-established hyphal network and be supplied with adequate phosphorus nutrition during early growth, which greatly improves the crop yield. 
Story: Two farms were testing new methods to increase production. Timber farm used AM fungi, while Pine farm used other conventional agricultural methods. 
Question: Which farm grew no cover crops?
[EX A]:
Pine.