问题 选择题

随着燃煤的价格不断上涨,少数不法商贩将煤矸石(矿井下与煤共生一处的石块)粉碎后掺在优质煤中高价销售给客户.为避免上当,最恰当的方法是检测下述物理量中的   

A.比热容

B.熔点

C.密度

D.热值

答案

答案:D

题目分析:优质煤和劣质煤的热值不同,燃烧相同的质量,释放的热量不同,优质煤释放的热量多,所以价位也高,所以不法商家将它们搀和在一起,谋取暴利,选D。

点评:解决本题的关键是熟知燃料燃烧的热值的含义

问答题

Passage 2 My wife Nane and I are both extremely happy to be with you today. I feel truly proud to belong to this extraordinary class of 2004, and I am pleased to see that so many parents and family members were here today. The day belongs to them, too. Without their constant support, understanding and sacrifice, none of us could have achieved what we have. For me, to receive a degree from Harvard is a very great honor indeed. There are few countries in the world whose leaders in public life, business, science and the humanities have not had some association with Harvard -- and no country that has not benefited from Harvard’s outstanding contributions to human knowledge.// You have invited me, I know, not as an individual, but as Secretary-General of the United Nations. You are saying that the United Nations matters, and that you want to hear what we have to say. Are you right in believing that the UN matters I think you are, because the UN offers the best hope of a stable world and a broadly equitable world order, based on generally accepted roles. That statement has been much questioned in the past year. But recent events have reaffirmed, and even strengthened, its validity. A role-based system is in the interest of all countries --especially today. Globalization has shrunk the world. The very openness, which is such an important feature of today’s most successful societies, makes deadly weapons relatively easy to obtain, and terrorists relatively difficult to restrain. //Today, the p feel almost as vulnerable to the weak as the weak feel vulnerable to the p. So it is in the interest of every country to have international rules and to abide by them. And such a system can only work if, in devising and applying the rules, the legitimate interests of all countries are accommodated, and decisions are reached collectively. That is the essence of multilateralism, and the founding principle of the United Nations. All great American leaders have understood this. That is one of the things that make this country such a unique world power. America feels the need to frame its policies, and exercise its leadership, not just in the light of its own particular interests, but also with an eye to international interests, and universal principles.// Among the finest examples of this was the plan for reconstructing Europe after World War Ⅱ, which General Marshall announced here at Harvard in 1947. That was one part of a larger-scale and truly statesmanlike effort, in which Americans joined with others to build a new international system -- a system which worked, by and large, and which survives, in its essentials, nearly 60 years later. During those 60 years, the United States and its partners developed the United Nations, built an open world economy, promoted human rights and decolonization, and supported the transformation of Europe into a democratic, cooperative community of states, such that war between them has become unthinkable.//

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