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问题 多项选择题

关于中洞法、侧洞法、柱洞法、洞桩法，说法正确的是()。

A.中洞法施工工序简单，施工引起的地面沉降较易控制 

B.侧洞法两侧洞施工时，中洞上方土体受多次扰动，中洞施工若不谨慎可能坍塌 

C.柱洞法的施工关键是如何确保两侧开挖后初期支护同步作用在顶纵梁上 

D.洞桩法是先挖洞，在洞内施作桩(柱)、梁和顶部结构，然后在其保护下施工 

E.侧洞法施T在处理中洞顶部荷载转移时，相对于中洞法要困难一些

答案

参考答案：B, C, D, E

填空题


The central problem of economics is to satisfy the people’s and nation’s wants. The problem we are faced with is that our (1) , here identified as money, are (2) . The only way we can resolve our (3) is to make choices. After looking at our resources, we must examine our list of (4) and identify the things we need (5) , those we can postpone, and (6) we cannot afford. As individuals, we face the central problem involved in economics — deciding just how to allocate our limited resources to provide ourselves with the greatest (7) of our wants.
Nations face the same problem. As a country’s population (8) , the need for more goods and services grows (9) . Resources necessary to production may increase, but there are (10) enough resources to satisfy the total desires of a (11) . Whether the budget meeting is taking place in the family living-room, in the conference room of the corporation (12) of directors, or in the chamber of the House of Representatives in Washington, the basic problem still exists. We need to find (13) of allocating limited resources in order to satisfy unlimited wants.
A short time ago, economists divided goods into two categories, free and economic. The former, like air and water, were in (14) abundance that economists had no concern about (15) of scarcity and what to do about it. Today many of these "free goods" are in (16) very expensive to use. Pollution has made clean air and water expensive for producers who have to filter their waste products, for consumers who ultimately pay for the producers’ extra costs, and (17) tax-payers who pay for the government’s involvement in cleaning the environment.
In the 1990s, almost all goods are (18) . Only by effort and money can they be (19) in the form people wish.
Meeting the needs of people and the demands from resources available leads to the basic activity of production. In trying to (20) unlimited wants from limited economic goods, production leads to new problems in economics.
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单项选择题

2008年实际外资最多的月份的合同外资约是实际外资最少的月份的合同外资的（）。

A．3.1倍

B．3.3倍

C．3.6倍

D．3.9倍
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