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: In the U.S., the majority of electricity is produced by burning coal or other fossil fuels. This causes air pollution, acid rain, and global warming. Fossil fuels are also limited and may eventually run out. Like fossil fuels, radioactive elements are limited. In fact, they are relatively rare, so they could run out sooner rather than later. On the other hand, nuclear fission does not release air pollution or cause the other environmental problems associated with burning fossil fuels. This is the major advantage of using nuclear fission as a source of energy. 
Story: Seattle produces a large amount of their electricity by burning fossil fuels due to the large presence of natural coal in the state. Jacksonville, on the other hand, has decreased their usage of fossil fuels used to produce electricity to low levels due to recent policy changes enacted by their state's government. 
Question: Which city, Seattle or Jacksonville, will have less acid rain?
[EX A]: Jacksonville.

[EX Q]: Background Paragraph: Cancer is a disease that causes cells to divide out of control. Normally, the body has systems that prevent cells from dividing out of control. But in the case of cancer, these systems fail. Cancer is usually caused by mutations. Mutations are random errors in genes. Mutations that lead to cancer usually happen to genes that control the cell cycle. Because of the mutations, abnormal cells divide uncontrollably. This often leads to the development of a tumor. A tumor is a mass of abnormal tissue. As a tumor grows, it may harm normal tissues around it. Anything that can cause cancer is called a carcinogen . Carcinogens may be pathogens, chemicals, or radiation. 
Story: A team of scientists studied two groups of mice. Group C was exposed to carcinogens, while group N was not. 
Question: Which group of mice had fewer abnormal cells divide uncontrollably?
[EX A]: group N.

[EX Q]: Background Paragraph: A dilution effect is seen when animals living in a group "dilute" their risk of attack, each individual being just one of many in the group. George C. Williams and W.D. Hamilton proposed that group living evolved because it provides benefits to the individual rather than to the group as a whole, which becomes more conspicuous as it becomes larger. One common example is the shoaling of fish. Experiments provide direct evidence for the decrease in individual attack rate seen with group living, for example in Camargue horses in Southern France. The horse-fly often attacks these horses, sucking blood and carrying diseases. When the flies are most numerous, the horses gather in large groups, and individuals are indeed attacked less frequently. Water striders are insects that live on the surface of fresh water, and are attacked from beneath by predatory fish. Experiments varying the group size of the water striders showed that the attack rate per individual water strider decreases as group size increases. 
Story: Kenya's Masai Mara wildebeest migration is one of the greatest spectacles in the natural world. Every year thousands of wildebeests cross the Mara river. John went to see the migration last year. He noticed that the wildebeests crossed the the river in a very large group. He noted that as case A. His guide told him that is not the case in other times of the year. The wildebeests cross the river in smaller groups in other times. John noted that as case B. The guide added that in both cases on thing is constant, they are attacked by the lions. 
Question: Which case would see the dilution effect working better, case A or case B?
[EX A]:
case A.