题干

我国古代把一种类似铲的挖土工具称为“镈”,在物物交换的时代,人们经常拿这种挖土工具去换取别的东西。但用这种东西交换比较麻烦,周景王便把这种农具小型化,铸成象征性的镈,它在以后的交换过程中充当了一般等价物,这就是原始的空首布。空首布在当时一定区域内所能起到的作用有(    )

①它可以表现其他一切商品的价值    ②它是商品交换发展到一定阶段的产物

③它能够充当商品交换的媒介  ④用它可以换回自己所需要的东西

A:①②③

B:①③④

C:②③④

D:①②④

上一题 下一题 0.0难度 选择题 更新时间:2017-03-20 02:46:30

答案(点此获取答案解析)

B

同类题2

任务型阅读

    Lindsay Renwick, the mayor of Deniliquin, a country town in New South Wales, misses the constant whir(嗡嗡声)of the rice mill whose giant fans dried the rice. The Deniliquin mill, the largest rice mill in the Southern Hemisphere (南半球), once processed enough grain to meet the needs of 20 million people globally. But six years of drought have had a destructive effect, reducing Australia's rice crop by 98 percent and leading to the mothballing of the mill last December.

    Drought affects every agriculture industry based in Australia, not just rice – from sheep farming, the country's other backbone, to the cultivation of grapes for wine, the fastest-growing crop there, with that expansion often coming at the expense of rice. The drought's effect on rice has produced the greatest impact on the rest of the world, so far. It is one factor contributing to skyrocketing prices, and many scientists believe it is among the earliest signs that a warming planet is starting to affect food production.

    Researchers are looking for solutions to global rice shortages – for example, rice that blooms earlier in the day, when it is cooler, to fight against global warming. Rice plants that happen to bloom on hot days are less likely to produce grains of rice, a difficulty that is already starting to emerge in inland areas of China and other Asian countries as temperatures begin to climb. 'there will be problems very soon unless we have new varieties of rice in place,” said Reiner Wassmann, climate change director at the International Rice Research Institute (IRRI). The recent reports on climate change carried a warning that could make the news even worse: that existing models for the effects of climate change on agriculture did not yet include newer findings that global warming could reduce rainfall and make it more variable.

    Yet the effects of climate change are not uniformly bad for rice. Rising concentrations (浓度) of carbon dioxide, the main greenhouse gas, can actually help rice – although the effect reduces or disappears if the plants face unnecessary heat, inadequate water, severe pollution or other stresses. Still, the flexibility of farmers here has persuaded some climate experts that, particularly in developed countries, the effects of climate change may be relieved, if not completely avoided. “I'm not as negative as most people,” said Will Steffen, director of the Fenner School of Environment and Society at Australian National University. “Farmers are learning how to do things differently.”

    Meanwhile, changes like the use of water to grow wine grapes instead of rice carry their own costs, as the developing world is discovering. “Rice is an essential food,” said Graeme Haley, the general manager of the town of Deniliquin. “Wine is not.”

Phenomenon

Six years of drought reduced Australia's rice crop by 98%, leaving the rice mill____

____of drought and climate change

Every Australian agriculture industry is affected,____from sheep farming to the cultivation of grapes for wine.

The whole world is in____of rice.

Prices rise____ .

Temperatures begin to climb, causing____rice production.

____to global rice shortages

Seek a new variety of rice that blooms earlier when it is cooler as a____

Some good news

Unless faced with unnecessary heat, inadequate water or other stress, the main green house gas can actually do____to rice.

Farmers are flexible and they can do things____.