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: One reason radiation is dangerous is that it can’t be detected with the senses. You normally can’t see it, smell it, hear it, or feel it. Fortunately, there are devices such as Geiger counters that can detect radiation. A Geiger counter, like the one in Figure below , has a tube that contains atoms of a gas. If radiation enters the tube, it turns gas atoms to ions that carry electric current. The current causes the Geiger counter to click. The faster the clicks occur, the higher the level of radiation. You can see a video about the Geiger counter and how it was invented at the URL below. 
Story: Robert and Thomas are visiting an abandoned amusement park in Russia that is rumored to emit radiation due to the materials used in the rides.  Robert visits the Ferris wheel and his Geiger counter clicks slowly. Thomas visits the merry go round and his Geiger counter begins to click rapidly. 
Question: Which person is in an area with higher levels of radiation?
[EX A]: Thomas.

[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.

[EX Q]: Background Paragraph: Geologists study earthquake waves to “see” Earth's interior. Waves of energy radiate out from an earthquake’s focus. These waves are called seismic waves ( Figure below ). Seismic waves go different speeds through different materials. They change speed when they go from one type of material to another. This causes them to bend. Some seismic waves do not travel through liquids or gases. They just stop. Scientists use information from seismic waves to understand what makes up the Earth’s interior. 
Story: Mary is studying the seismic waves of a recent earthquake from 2 locations around its focus. She notes at point A the waves are easily detectable. at point B the waves are unable to be read at all, as if they just stopped. 
Question: Given Mary decides to check the readings for two other locations, points C and D, and notices the waves at D are slower, will the areas underground at points C and D be made of the same materials or different materials?
[EX A]:
different.