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.
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Question: 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: Mike is studying the predator prey relationship. He is specifically studying three species, species A, species B, and species C. Species A is a predator; species B is the prey; and species C is a plant species that species B lives on. Mike now needs to figure out how the predator prey relationship balance the ecosystem.
Question: If species C population decrease, would it affect the ecosystem positively or negatively?

Answer: negatively.

Question: Background Paragraph: Huge amounts of chemicals, such as fertilizers and pesticides, are applied to farm fields (see Figure below ). Some of the chemicals are picked up by rainwater. Runoff then carries the chemicals to nearby rivers or lakes. Dissolved fertilizer causes too much growth of water plants and algae. This can lead to dead zones where nothing can live in lakes and at the mouths of rivers. Some of the chemicals can infiltrate into groundwater. The contaminated water comes up in water wells. If people drink the polluted water, they may get sick.
Story: Jimbo and Jedd are both farmers who have lakes and water wells downstream from their farms. Jimbo's products have been in high demand recently, so he has started to use very high amounts of fertilizers on his farms. Jedd has recently decreased the amount of fertilizer he uses because his products aren't wanted as much by the people in his town.
Question: Who will be less likely to contaminate their respective water wells?

Answer: Jedd.

Question: Background Paragraph: In the long term, the greatest changes in the Solar System will come from changes in the Sun itself as it ages. As the Sun burns through its supply of hydrogen fuel, it gets hotter and burns the remaining fuel even faster. As a result, the Sun is growing brighter at a rate of ten percent every 1.1 billion years. In about 600 million years, the Sun brightness will have disrupted the Carbon Cycle to the point that trees and forests (C3 photosynthetic plant life) will no longer be able to survive and in around 800 million years, the Sun will have killed all complex life on the Earth's surface and in the oceans. In 1.1 billion years' time, the Sun's increased radiation output will cause its circumstellar habitable zone to move outwards, making the Earth's surface too hot for liquid water to exist there naturally. At this point, all life will be reduced to single celled organisms. Evaporation of water, a potent greenhouse gas, from the oceans' surface could accelerate temperature increase, potentially ending all life on Earth even sooner. During this time, it is possible that as Mars's surface temperature gradually rises, carbon dioxide and water currently frozen under the surface regolith will release into the atmosphere, creating a greenhouse effect that will heat the planet until it achieves conditions parallel to Earth today, providing a potential future abode for life. By 3.5 billion years from now, Earth's surface conditions will be similar to those of Venus today.
Story: Rob knows a brilliant scientist who has made a time machine. One day, the scientist let Rob travel time with his machine. Rob noticed that the machine had four gears, gear A, gear B, gear C, and gear D. Rob started with Gear A, which represented the present time. Then he pushed the gear to gear B, which was 600 million years from now. Then he further pushed the gear to gear C, which brought him to 800 million years from now. Finally, he pushed the gear to gear D, which brought him to 1.1 billion years from now. Though he traveled time, Rob was always on Earth all the time.
Question: Would he see less or more plant species in gear A than in gear B?

Answer:
more.