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: Depleted soils can be protected from soil erosion by groundcover plants such as naturally growing grasses in agroforestry systems. These help to stabilise the soil as they increase cover compared to short-cycle cropping systems. Soil cover is a crucial factor in preventing erosion. Cleaner water through reduced nutrient and soil surface runoff can be a further advantage of agroforestry. The runoff can be reduced by decreasing its velocity and increasing infiltration into the soil. Compared to row-cropped fields nutrient uptake can be higher and reduce nutrient loss into streams.Further advantages concerning plant growth:. 
Story: Two neighboring farms both had depleted soils due to intensive agricultural practices for decades. Apple far decided to start an agroforestry system and other methods to protect their depleted soils, while Pear farm did nothing and had big losses the following years. 
Question: Which farm didn't reduce the runoff?

Answer: Pear.


Question: Background Paragraph: Generally, nearsightedness first occurs in school-age children. There is some evidence that myopia is inherited. If one or both of your parents need glasses, there is an increased chance that you will too. Individuals who spend a lot of time reading, working or playing at a computer, or doing other close visual work may also be more likely to develop nearsightedness. Because the eye continues to grow during childhood, myopia typically progresses until about age 20. However, nearsightedness may also develop in adults due to visual stress or health conditions such as diabetes. A common sign of nearsightedness is difficulty seeing distant objects like a movie screen or the TV, or the whiteboard or chalkboard in school. 
Story: David is a doctor who works for the public health department. After analyzing health data for his city, he found twenty percent of the population have myopia. He categorized them as group A. Another eighty percent didn't have myopia. He put them in group B. He now needs to devise a plan on how to tackle myopia in his city. 
Question: Would group A find it easier or harder to see distant objects than group B?

Answer: harder.


Question: Background Paragraph: In common everyday speech, speed of sound refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance: sound travels most slowly in gases; it travels faster in liquids; and faster still in solids. For example, (as noted above), sound travels at 343 m/s in air; it travels at 1,480 m/s in water (4.3 times as fast as in air); and at 5,120 m/s in iron (about 15 times as fast as in air). In an exceptionally stiff material such as diamond, sound travels at 12,000 metres per second (27,000 mph);[1] (about 35 times as fast as in air) which is around the maximum speed that sound will travel under normal conditions. 
Story: John and Keith are neighbors. They have been pondering about how to communicate with each other in a doomsday scenario when all the electronic devices would be useless. They connected their houses with three ducts. 
One of the ducts is filled with air; they called it channel A. Another duct is filled with water; they 
called it channel B. And the last duct is filled with iron; they called it channel C. They can now transmit sound with these channels of communication; in case, disaster strikes. 
Question: Which channel would be the slowest, channel A,  channel B, or channel C?

Answer:
channel A.