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: Ocean acidification occurs when excess carbon dioxide in the atmosphere causes the oceans to become acidic. Burning fossil fuels has led to an increase in carbon dioxide in the atmosphere. This carbon dioxide is then absorbed by the oceans, which lowers the pH of the water. Ocean acidification can kill corals and shellfish. It may also cause marine organisms to reproduce less, which could harm other organisms in the food chain. As a result, there also may be fewer marine organisms for humans to consume. 
Story: Two islands were situated in different oceans. Hill island used fossil fuels and released a lot of carbon dioxide into the atmosphere, while Coral island was very protective towards the air and the ocean. 
Question: Which island contributed less to the death of shellfish?

Answer: Coral.


Question: Background Paragraph: For comparison,  sunlight on Saturn is slightly brighter than Earth sunlight at the average sunset or sunrise (see daylight for comparison table). Even on Pluto, the sunlight would still be bright enough to almost match the average living room. To see sunlight as dim as full moonlight on Earth, a distance of about 500 AU (~69 light-hours) is needed; there are only a handful of objects in the Solar System known to orbit farther than such a distance, among them 90377 Sedna and (87269) 2000 OO67. 
Story: A startup has build a simple spaceship that uses only sunlight for its propulsion. The more sunlight it gets faster it moves. They planned to send the spaceship to three different points, point A, point B, and point C. Point A is near the planet Saturn, point B is near Pluto, and point C is about 69 light-hours away. 
Question: At which point the spaceship would move faster, point B or point C?

Answer: point B.


Question: Background Paragraph: Rainfall in an area is important because it influences the rate of weathering. More rain means that more rainwater passes through the soil. The rainwater reacts chemically with the particles. The top layers of soil are in contact with the freshest water, so reactions are greatest there. High rainfall increases the amount of rock that experiences chemical reactions. High rainfall may also carry material away. This means that new surfaces are exposed. This increases the rate of weathering. 
Story: John was studying about the history of Sahara desert. He was amazed to find that ten thousand years ago there were plenty of rainfall in that region. He labeled that era as era A. Then he found that rainfall deceased in the region about eight thousand years ago. He labeled that era as era B. He was wondering how that change in rainfall might have helped emerge the Egyptian civilization. 
Question: In which era new surfaces would be exposed, era A or era B?

Answer:
era A.