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I'm taking a test and have to guess the right answer to the question after the article. Article: More and more people take part in marathons these days - over 30,000 people will run the London Marathon this weekend, for instance. But it's not just the 26 miles and 385 yards that could be a daunting prospect. "I have to admit to being completely frustrated by the blocking and for 18-19 miles was just keeping away from people and being held up," one participant grumbled after the 2012 London Marathon. "I had to overtake a lot of people and ended up with bruised forearms from all the elbows," said another. How do such crowding problems arise, and could they be reduced? Some researchers believe that we can find the answers through a more familiar system in which jams appear - road traffic flow. Martin Treiber, of the Technical University of Dresden in Germany, has previously developed models for traffic flow. One of the first attempts to model traffic flow was made in the 1950s by James Lighthill and his collaborator Gerard Whitham of Manchester University. They considered the traffic as a kind of liquid flowing down a pipe, and looked at how the flow changes as the fluid gets denser . At first the flow rate increases as the density increases, since you simply get more stuff through in the same period of time. But if the density becomes too high, there's a risk of jams, and the flow rate drops sharply. Treiber's model of a marathon uses this same principle that the flow rate first increases and then decreases as the density of runners increases, thanks to an sudden switch from free to crowded flow. He assumes that there is a range of different preferred speeds for different runners, which each maintains throughout the race. With just these factors, Treiber can calculate the flow rate of runners, knowing the "carrying capacity" at each point on the route. This allows Treiber to figure out how blocking might depend on the race conditions - for example, for different starting procedures. Some marathons start by letting all the runners set off at once (which means those at the back have to wait until those in... Question: What's the main idea of the passage? Options: A: Make a comparison between marathon and road traffic. B: Running a marathon is somewhat dangerous if it is not well organized. C: Introduce a new technology to solve the blocking problem in marathon. D: Some advice for people who are to run a marathon.
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C

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I'm taking a test and have to guess the right answer to the question after the article. Article: When you think about math, you probably don't think about breaking the law, solving mysteries or finding criminals. But a mathematician in Maryland does, and he has come up with mathematical tools to help police find criminals. People who solve crimes look for patterns that might reveal the identity of the criminal. It's long been believed, for example, that criminals will break the law closer to where they live, simply because it's easier to get around in their own neighborhood. If police see a pattern of robberies in a certain area, they may look for a suspect who lives near the crime scenes. So, the farther away from the area a crime takes place, the less likely it is that the same criminal did it. But Mike O'Leary, a mathematician at Towson University in Maryland, says that this kind of approach may be too simple. He says that police may get better clues to the location of a criminal's home base by combining these patterns with a city's layout and historical crime records. The records of past crimes contain geographical information and can reveal easy targets -- that is, the kind of stores that might be less difficult to rob. Because these stores are along roads, the locations of past crimes contain information about where major streets and intersections are. O'Leary is writing a new computer program that will quickly provide this kind of information for a given city. His program also includes information about the people who live in the city, and information about how a criminal's patterns change with age. It's been shown, for example, that the younger the criminal, the closer to home the crime. Other computer programmers have worked on similar software, but O'Leary's uses more math. The mathematician plans to make his computer program available, free of charge, to police departments around the country. The program is just one way to use math to fight crime. O'Leary says that criminology -- the study of crime and criminals -- contains a lot of good math problems. "I feel like I'm in a gold mine and ,"... Question: By "I'm the only one who knows what gold looks like", O'Leary means that he _ . Options: A: is better at finding gold than others B: is the only one who uses math to make money C: knows more criminals than other mathematicians D: knows best how to use math to help solve crimes
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D

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I'm taking a test and have to guess the right answer to the question after the article. Article: Squirrels often communicate with whistles, chirps and chucks, which sound like the word "chuck". Whistles and chirps are like the sounds that many birds make.Now scientists have translated some of their squirrel-speak. Hare, a professor of zoology at the University of Maniloha in Winnipeg, and his team managed to record squirrels' alarm calls.The researchers studied the sounds and then played them back to 60 wild squirrels, which the scientists approached individually with a video recorder to capture their reponses.Some squirrels lifted their heads up and became.Alert .Creatures that were more frightened simply ran for their lives and dived into caves. "In effect then, whistles that mix with chucks say 'there's an enemy of average threat that's here', and whistles without chucks say 'there's an enemy of seemingly average threat around here somewhere', while pure chirps say, 'I'm hiding here because there's an immediate danger.' " Hare told.Discovery News. Hare and some other researchers believe such sounds arc part of an advanced language that develops just as all other communication systems. Although squirrels risk their lives when they call out to warn others of threats, other squirrels might admire this behaviour, thus increasingly the caller's social status, like humans who look up to heroes. Hare added that other animals, such as birds, probably understand at least some squirrel language, since they also may benefit from the alarm calls. In fact, another Canadian study found that deep-voiced, black-capped chickadees have their own language too.According to certain research, there are a lot of tidings in chickadees' calls, such as directing fellows' activities, keeping in contact between mates, and raising alarms. While chickadees and other birds are often welcomed into gardens by homeowners, squirrels are frequently viewed as pests . Hare wishes a greater understanding of the complex social lives and communication systems of squirrels will provide "hope that humans will gain a greater appreciation and... Question: The text mainly talks about Options: A: the study on the language of squirrels B: the comparison between squirrels and chickadees C: the calling for the protection of squirrels D: the ways for squirrels to escape from their enemies
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A