13.According to the speaker, what does the average negotiator usually do?
Passage 2
To most of us sharks are the most dangerous fish in the sea and they attack humans. However, according to Doctor Clark, who has studied the behavior of sharks for twelve years, humans are not normally on the shark's menu. What do sharks feed on, mainly fish and other sea animals? Doctor Clark also found that sharks don't eat as much food as people think. For instance, a nine-year-old shark only needs two pound of food a day to keep healthy. But she says, sharks sometimes starve and at other times they fill themselves with what they have killed. Around the world, there are only about one hundred shark attacks on humans each year, ten of which proved fatal. But consider this, in the US alone, about three million people are bitten by dogs each year. Of these, thirty people die. If sharks bite you, says Doctor Clark, the reason is usually because of the mistake you ****natural food. For example, say you went underwater-fishing and saw a shark, you could be in trouble. The shark might go for the injured fish you had attacked and take a bite of you at the same time. If you go into a shark's territory and threaten it, it might try to bite you. That's because sharks are territorial and tend to guard their territory. Like dogs, they protect the area they think is their own.
14.What does the passage say about the eating behavior of sharks?
15.When might a shark attach humans?
16.What do we learn from the passage about sharks?
Passage 3
Science fiction writers have often imagined humans going to live on the Mars. But these days, scientists are taking the idea seriously. It has a great deal to recommend it, since it might solve the problem of overcrowding on the earth. But obviously, it would not be worth making the effort unless people could live there naturally. If the atmosphere were like that of the earth, this might be possible. But in fact it is mostly carbonoxidite. Apart from that, there are other problems to be overcome. For example, the temperature would have to be raised from 6 degrees below zero to 15 degrees above it. Scientists who study Mars have laid down the program that they can follow. To begin with, they will have to find out whether life has ever existed on the planet of Mars in the past. Secondly they will have to make a reliable map of its surface. And finally, they will have to make a list of the gases. Above all, they will have to discover how much nitrogen it possesses. Since nitrogen is four fifths of the air we breathe, they are surprising optimistic about raising the temperature on Mars and believe it could be down in hundred years. It will take a bit longer, though, to transform the atmosphere so that human beings could live there. Scientists estimate this will take one hundred thousand years.
17.Why are scientists interested in Mars?
18.What is the one of the things that must be done if a man can live on Mars?
19.Why do scientist want to find out whether there is sufficient nitrogen on Mars?
20.What is the prospect of people living on Mars?
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