（）是指证券市场行情周期性变动而引起的风险。 A．政策风险  B．经济周期波动风险

Malthusian fears that population growth will outstrip food supplies have been widely discounted as food production has kept well ahead of growing human numbers in the last half century. While population doubled, food supply tripled, and life expectancy increased from 46 in the 1950s to around 65 today. But more recently, some experts have once again been sounding the alarm about a possible food crisis.

The reason lies in the combined impact of many factors including climate change, forest denudation, land degradation, water shortage, declining oil supplies, species extinction, destruction of coastal ecosystems and the growing demands for a meat-rich diet from newly developed parts of the world.

At the root of all these problems has been the ruthless exploitation of the earth’s resources, fuelled by growing affluence in some parts of the world and desperate poverty in others. Between 1980 and 2000, global population rose from 4.4 billion to 6.1 billion, while food production increased 50 per cent. By 2050, the population is expected to reach 9 billion.

Data shows that while grain yields per acre have been increasing, the rate of increase has been slowing since the days of the Green Revolution in the 1970s. Most of the benefits of irrigation, machinery, fertilizer and plant breeding have already been realized. The production of grain per acre is close to the maximum obtainable through photosynthesis.

To keep up with the growth in human population, more food will have to be produced over the next 50 years than has been during the past 10,000 years combined, said the participants of the recent UN-backed forum in Iceland on sustainable development. It is, of course, possible that new technologies, smart environmental management and sensitive social policies will combine to good effect to usher in a new green revolution. But as grain reserves have fallen to their lowest level for many years, this cannot be guaranteed.

At the 1996 World Food Summit political leaders from 186 countries pledged to halve the number of hungry people in the world by the year 2015, or a reduction of 20 million each year. At that time, about 800 million people were reported to suffer from under- nourishment. In 2007 estimates from the UN Food and Agriculture Organization (FAO) suggest that there are 854 million people who do not get enough to eat every day. "Far from decreasing, the number of hungry people in the world is currently increasing," said FAO Director-General Jacques Diouf. (Of course, world population has increased by some 800 million in that time, so food supplies have kept up relatively well, but have failed to reach an increasing number, let alone reduce the total going hungry.)

According to the passage, the Green Revolution in the 1970s（）

A. witnessed the slowing down of the increase of grain output

B. caused many innovative measures to be taken to promote crop production

C. appeared as the environmental situation degraded

D. reached a record high in food production

双肾积水最常见的原因为

A．双输尿管狭窄

B．输尿管结石

C．下尿路梗阻

D．膀胱肿瘤

E．输尿管畸形

贯彻正规系统原则，必须严格依法治训，（），克服训练中的盲目性和随意性。

A、按标施训

B、按纲施训

C、按质施训

D、按量施训

For each blank, choose the best answer from the four choices and write down on the answer sheet.

It is claimed that Al applications have moved from laboratories to the real world. However, conventional von Neumann computers are (1) for Al applications, because they are de- signed mainly for numerical processing. In a larger yon Neumann computer, there is a larger ratio of memory to processing power and consequently it is even less efficient. This (2) remains no matter how fast we make the processor because the length of the computation becomes dominated by the time required to move data between (3) and memory. This is called the yon Neumann (4) . The bigger we build the machines, the worse it gets. The way to solve the problem is to diverse from the traditional architectures and to design special ones for Al applications. In the research of future Al architectures, we can take advantages of many (5) or currently emerging concepts. in computer architecture, such as dataflow computation, stack machines, tagging, pipelining, systolic array, multiprocessing, distributed processing, database machines, and inference machines.

2（）

A．efficiency

B．condition

C．inefficiency

D．situation

社会政治制度的发展、演变，丰富了人类文明的内涵。阅读材料，回答问题。

材料一封建诸侯，各君其国，卿大夫亦世其官……其后积弊日甚，其势不得不变。于是先从在下者（平民）起……此已开后世布衣将相之例……秦皇尽灭六国以开一统之局……下虽无世禄之臣，而上犹是继体之主（最高统治者仍由王族世袭）也。

汉祖以匹夫起事，角群雄而定一尊。其君既起自布衣，其臣亦自多亡命……天下之变局，至是始定。

——赵翼《廿二史札记》

材料二1781年经13州批准的《邦联和永久联合条例》生效，标志着美国成为一个邦联制国家。它规定：“各州均保留其主权、自由与独立。”但实践证明了它的不可行性，美国迫切需要新的政治制度挽救国家。1787年的费城制宪会议完成了这一历史使命。它创造了一种新的政治制度模式，即联邦制。明确提出了新的中央政府即联邦政府与州政府行使权力所遵循的四条基本原则：分权原则；共有权原则；权力禁区原则；宪法至上原则。1788年，新宪法经各州批准生效。至此，联邦制在美国正式确立。这一制度被人们认为是“自由和绝对统治之间最成功的调和”。

——摘编自张定河《美国联邦制的基本原则及其历史演变》

材料三回溯中国近代以来的历史，中国人民为争取民主进行了百折不挠的斗争和艰难探索，但只有在中 * * 党的领导下，才真正获得了当家作主的权利。……自20世纪70年代末实行改革开放政策以来，中国在深化经济体制改革的同时，坚定不移地推进政治体制改革，中国的民主制度不断健全，民主形式日益丰富，人民充分行使当家作主的权利。

——《中国的民主政治建设》白皮书

依据材料一，说明“天下之变局”是指什么？结合所学知识，概括由西周至秦汉国家政治体制发生的变化。