题目内容
Participation in the Olympic Games is looked upon as an honor as well as an achievement.
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The United States of America is among the top 10 countries.
Don't Count on Dung
Conservationists （自然保护主义者） may be miscalculating the numbers of the threatened animals such as elephants, say African and American researchers. The error occurs because of a flaw in the way they estimate animal numbers from the piles of dung （粪） the creatures leave behind.
The mistake could lead researchers to think that there are twice as many elephants as there really are in some regions, according to Andrew Plumptre of the Wildlife Conservation Society （WCS） in New York.
Biologist Katy Payne of Cornell University in Ithaca, New York, agrees. "We really need to know elephant numbers and the evidence that we have is quite indirect," says
Payne, who electronically tracks elephants.
Counting elephants from planes is impossible in the vast rainforests of Central Africa. So researchers often estimate elephant numbers by counting dung piles in a given area.
They also need to know the rate at which dung decays. Because it's extremely difficult to determine these rates, however, researchers counting elephants in one region tend to rely on standard decay rates established elsewhere.
But researchers at the WCS have found that this decay rate varies from region to region depending on the climate and environment. Using the wrong values can lead the
census astray （离开正道）, says Plumptre.
He and his colleague Anthony Chifu Nchanji studied decaying elephant dung in the forests of Cameroon. They found that the dung decayed between 55 and 65 per cent more slowly than the dung in the rainforests of neighbouring Gabon. If researchers use decay rates from Gabon to count elephants in Cameroon, they would probably find more elephants than are actually around.
This could mean estimates in Cameroon are at least twice as high as those derived from decay rates calculated locally, says Plumptre. "However accurate your dung density estimate might be, the decay rate can severely affect the result."
Plumptre also says that the dung-pile census should be carried out over a region similar in size to an elephant's natural range. The usual technique of monitoring only small, protected areas distorts numbers because elephants move in and out of these regions, he says. "If the elephant population increases within the protected area, you can not determine whether it is a real increase or whether it is due to elephants moving in because they are being poached （入侵偷猎） outside."
Plumptre says that similar problems mayalso affect other animal census studies that rely on indirect evidence such as nests, tracks or burrows （地洞）.
第 37 题 The word "threatened" in the first sentence of the first paragraph could be best replaced by.
我国《票据法》规定，票据行为包括（）。
Cost as a Factor in Supply
In a purely competitive market, the supplier of goods and services has no control over the market price, because he produces too little to influence market conditions. With no difference between his products and the products_____（51） his competitors, he will sell nothing if he charges above the market price and he will sell all if he charges at or_____（52） the market price. However, in considering the price, he must take the_____（53） of production into consideration. There are times when he may be willing to sell below his cost. This might happen when prices tumble for_____（54） he believes will be a short time. However, no business person can_____（55） to lose money for a prolonged period. He must be constantly_____（56） of his costs in relation to the market price if he is to compete successfully and earn a profit.
Many people have the impression that as production increases, costs per unit decrease._____（57） mass production has made this true in certain industries and at certain levels of production_____（58） logic and practical experiences have shown that costs per unit begin to rise beyond a certain level of production. Some economists_____（59） to this principle as the law of increasing costs.
The reason costs rise as production goes up is_____（60）. However, it is easy to recognize that as production goes up, the need for additional factors of production will also grow,_____（61） competitive bidding in the marketplace for the factors of production. If a producer needs_____（62） skilled labor to produce more, and none of this labor is unemployed, the producer will have to get_____（63） from other sources. This can be done by_____（64） higher wages. Higher bidding would also apply to the other factors of production. We must also recognize that not all labor is equally productive,_____（65） not all land is equally fertile and not all ore （矿石） is equally rich in the mineral wanted.
第 51 题
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