能引起个体动机并满足个体需要的外在刺激称为________。

正方形ABCD的边长为1．如果将线段BD绕着点B旋转后，点D落在BC延长线上的点D′处，那么tan∠BAD′=______．

进行水力模型试验时，要实现有压管流的动力相似，应选用的相似准则是( )。

A．(A) 雷诺准则

B．(B) 弗劳德准则

C．(C) 欧拉准则

D．(D) 韦伯准则

在三角形的每条边上各取三个分点（如图2.6.2所示），以这9个分点为顶点可画出若干个三角形．若从中任意抽取一个三角形，则其三个顶点分别落在原三角形的三条不同边上的概率为（）。

A.A

B.B

C.C

D.D

E.E

如果某客户成长性资产占56%，则该客户属于（ ）。

A．轻度保守型

B．中立型

C．轻度进取型

D．进取型

As the importance of recycling becomes more apparent, questions about it linger. Is it worth the effort How does it work Is recycling waste just going into a landfill in China Here are some answers.
It is an awful lot of rubbish. Since 1960 the amount of municipal waste being collected in America has nearly tripled, reaching 245m tonnes in 2005. According to European Union statistics, the amount of municipal waste produced in western Europe increased by 23% between 1995 and 2003, to reach 577kg per person. (So much for the plan to reduce waste per person to 300kg by 2000.) As the volume of waste has increased, so have recycling efforts. In 1980 America recycled only 9.6% of its municipal rubbish ; today the rate stands at 32%. A similar trend can be seen in Europe, where some countries, such as Austria and the Netherlands, now recycle 60% or more of their municipal waste. Britain’s recycling rate, at 27%, is low, but it is improving fast, having nearly doubled in the past three years.
Even so, when a city introduces a kerbside recycling programme, the sight of all those recycling lorries trundling around can raise doubts about whether the collection and transportation of waste materials requires more energy than it saves. "We are constantly being asked: Is recycling worth doing on environmental grounds " says Julian Parfitt, principal analyst at Waste & Resources Action Programme (WRAP), a non-profit British company that encourages recycling and develops markets for recycled materials.
Studies that look at the entire life cycle of a particular material can shed light on this question in a particular case, but WRAP decided to take a broader look. It asked the Technical University of Denmark and the Danish Topic Centre on Waste to conduct a review of 55 life-cycle analyses, all of which were selected because of their rigorous methodology. The researchers then looked at more than 200 scenarios, comparing the impact of recycling with that of burying or burning particular types of waste material. They found that in 83% of all scenarios that included recycling, it was indeed better for the environment.
Based on this study, WRAP calculated that Britain’s recycling efforts reduce its carbon-dioxide emissions by 10m-15m tonnes per year. That is equivalent to a 10% reduction in Britain’s annual carbon-dioxide emissions from transport, or roughly equivalent to taking 3.5m cars off the roads. Similarly, America’s Environmental Protection Agency estimates that recycling reduced the country’s carbon emissions by 49m tonnes in 2005.
Recycling has many other benefits, too. It conserves natural resources. It also reduces the amount of waste that is buried or burnt, hardly ideal ways to get rid of the stuff. (Landfills take up valuable space and emit methane, a potent greenhouse gas; and although incinerators are not as polluting as they once were, they still produce noxious emissions, so people dislike having them around.) But perhaps the most valuable benefit of recycling is the saving in energy and the reduction in greenhouse gases and pollution that result when scrap materials are substituted for virgin feed-stock. "If you can use recycled materials, you don’t have to mine ores, cut trees and drill for oil as much," says Jeffrey Morris of Sound Resource Management, a consulting firm based in Olympia, Washington.
Extracting metals from ore, in particular, is extremely energy-intensive. Recycling aluminium, for example, can reduce energy consumption by as much as 95%. Savings for other materials are lower but still substantial: about 70% for plastics, 60% for steel, 40% for paper and 30% for glass. Recycling also reduces emissions of pollutants that can cause smog, acid rain and the conta-mination of waterways.