单选题Since the 1930s, the idea that creatures might advertise their " fitness " as mates through symmetry has been around. It rests on the notion that factors ranging from bad genes to coming off worse in too many fights will lead to asymmetries others can see. And over the past few years, experiments with animals and humans seemed to support the idea that symmetry in features such as plumage and facial characteristics influences mate selection. But no one had actually checked that the animals in these experiments can actually see the subtle differences in symmetry, typically of between 1 and 2 percent. Now the first such experiment has been carried out. The results are worrying for advocates of symmetry detection as a powerful factor in mate selection. John Swaddle, an ethnologist at the University of Bristol, performed the experiment using wild starlings, which have excellent eyesight. He trained them to hit keys marked with bar patterns with varying levels of asymmetry in order to receive food rewards. This showed the starlings could easily detect asymmetries of between 5 and 10 percent. But at between 1 and 2 percent, their performance plummeted to no better than random guessing. " This suggests that the levels of asymmetry that birds encounter in nature will often be just too small to be detected, " says Swaddle. He says experiments that linked small asymmetries to fitness may have produced misleading correlations, and says the only direct evidence that birds use asymmetry as a cue to mate fitness involves levels of asymmetry of at least 10 percent. " I think signaling by asymmetry will probably only occur when species show such very large asymmetries—and this doesn't occur that often. " This raises questions about research suggesting that humans are influenced by visual asymmetry in their choice of partner. Michael Butt of the Perception Laboratory at the University of St. Andrews, who has carried out such experiments, concedes that no one has ever checked if humans have a threshold to asymmetry detection. He thinks a conclusive test of this would probably involve manipulating complex three-dimensional images: " It would be a very difficult experiment to do " Burt adds that the abilities of animals to detect asymmetry in bar patterns may not reflect their talent for spotting asymmetries in body shape. " The visibility of an asymmetry may well depend on its type, " he says. Swaddle agrees, and is planning further experiments. " But I suspect that asymmetry is used as a visual cue less often than most people appear to presume, " he warns.

填空题微观经济学研究社会中单个经济单位的经济行为，考察他们的选择。这些单个经济单位包括______、______。______是产品和劳务的消费者，一是产品和劳务的生产者和提供者。

单选题Egyptian wine has an extensive history within the history of Egyptian civilization. Grapes were not (1) to the landscape of Egypt, rather the vines themselves are (2) to have been imported from the Phoenicians, (3) the actual origins remain in (4) . What is known, is that (5) the third millennium BC, Egyptian kings of the first (6) had extensive wine cellars, and wine was used extensively in the temple ceremonies. The main (7) of wine in Egypt, took place between the king, nobles, and the priests in temple ceremonies, and is (8) by numerous painted relief's, and other (9) evidence. The vineyards of ancient Egypt, were quite different from the modern methods of wine making today. (10) viticulture ( or wine making), ceased to (11) an exclusively ceremonial purpose, the Egyptians began to experiment with simple structures for their vines to train on, (12) found a way to train their vines so they were easy low (13) bushes, and found ways for the soil to (14) more moisture for the vines. Egyptian wine making experiments included the use of different wine presses, adding heat to the must ( the grape juice ready for fermentation) (15) make the wine sweet, and differences in vat types and materials. The (16) finished product of wine, was poured through a cloth filter, and then into earthenware jars, (17) they would be sealed with natural tar and left to (18) . The Egyptians kept accurate records of their vintages, and (19) of their wines, each jar of wine was clearly (20) with it's own vintage, and quality.

填空题资源的稀缺性是相对于______而言的。

填空题一种商品的需求是指消费者在一定时期内在______的价格下______而且______的该种商品的数量。

填空题消费者的实际收入不变的情况下，不同商品之间的价格相对变动所引起的某种商品的需求量的变动称为______。

填空题边际技术替代率可以转换成______之比。

填空题消费者剩余是指消费者愿意为某种商品或劳务支付的价格与其______支付的价格之间的差额。

填空题“经济人”最早是由______阐释的。此人还提出了“看不见的手”著名思想。

填空题用公式表示生产要素最佳组合的条件______。

填空题当供求力量自由作用时，某年的谷物歉收会引起______上升。

填空题微观经济学中使用了定量和定性分析方法，其中定量分析方法主要有______边际分析和增量分析等。

填空题两种生产要素增加所引起产量变动的情况可以分为______、______、______3个阶段。

填空题认为效用可以度量的理论是______，而认为效用不可以度量只可以排序的理论是______。

单选题Current Group, a Germantown-based technology firm, has taken over an ordinary looking house in Bethesda and turned it into a laboratory for smart-grid technology, the system the company believes will bring the nation's electricity grids into the digital age. In the front yard stands a utility pole hooked up to a special transformer that connects the power lines to high-speed Internet. Hundreds of sensors attached to the lines monitor how power flows through the home. That information is then sent back to the utility company. The process lets a utility more efficiently manage the distribution of electricity by allowing two-way communication between consumers and energy suppliers via the broadband network on the power lines. Based on data they receive from hundreds of homes, utilities can monitor usage and adjust output and pricing in response to demand. Consumers can be rewarded with reduced rates by cutting back on consumption during peak periods. And computerized substations can talk to each other so overloaded circuits hand off electricity to those that have not fully loaded, helping to prevent blackouts. Some utility companies have launched initiatives to give consumers data about their energy consumption habits in an effort to lower energy bills. Smart-grid technology takes such programs further by automating electricity distribution, which would make grids more reliable and efficient. By partnering with utilities, the company hopes to tap into $4.5 billion in stimulus grants intended to encourage smart-grid development. When he announced the funding, President Obama pointed to a project in Boulder, Colo. , as an example of a successful smart-grid experiment. Current is one of the companies working on the project. Current's chief executive Tom Casey believes the technology will help utility companies better distribute electricity produced by renewable resources, such as solar panels or wind farms. " A smart grid's system can be paired up with the renewable resources so that when the renewable source is varying, the overall load can be varied as well, " Casey told the House Select Committee on Energy Independence and Global Warming. " This will reduce or eliminate the need for backup coal or gas-based power generation plants. /

填空题生产一定量某种产品所需要的各种生产要素的配合比例称为— —。

填空题边际产量曲线与平均产量曲线相交于平均产量曲线的______。相交之前，MP______AP，在相交之后，MP______AP。

填空题在消费者______收入保持不变的情况下，由于价格变化引起的______收入变动所引起的商品需求量的变化称为收入效应。

填空题生产可能性曲线可以说明资源配置效率，如果增加一种物品的产量就必须同时______其他物品的产量。

填空题边际替代率是______曲线的斜率的绝对值，边际替代率是递减的，原因在于______规律。