问题 选择题

下列物质的应用,利用的性质与其它三种有本质区别的是

A.用金属丝做导线

B.用醋酸除去茶壶中的水垢

C.用熟石灰改良酸性土壤

D.用明矾净化水

答案

答案:A

A.金属丝可作导线,是利用金属具有良好的导电性,体现出来的性质是物理性质;

B.茶壶中的水垢主要成分是碳酸钙,醋酸和碳酸钙生成醋酸钙和二氧化碳和水,说明体现出来的性质是化学性质;

C.利用熟石灰改良酸性土壤,是利用氢氧化钙与酸反应,属于化学变化,体

D. 用明矾净化水,明矾与水反应生成氢氧化铝胶体,是化学变化,现出来的性质是化学性质;

故选A。

单项选择题
单项选择题

The question of whether war is inevitable is one, which has concerned many of the world’s great writers. Before considering this question, it will be useful to introduce some related concepts. Conflict, defined as opposition among social entities directed against one another, is distinguished from competition, defined as opposition among social entities independently striving for something, which is in inadequate aupply. Competitors may not be aware of one another, while the parties to a conflict are. Conflict and competition are both categories of opposition, which has been defined as a process by which social entities function is the disservice of one another.

Opposition is thus contrasted with cooperation, the process by which social entities function in the service of one another. These definitions are necessary because it is important to emphasize that competition between individuals or groups in inevitable in a world of limited resources, but conflict is not. Conflict, nevertheless, is very likely to occur, and is probably an essential and desirable element of human societies.

Many authors have argued for the inevitability of war from the premise that in the struggle for existence among animal species, 0nly the fittest survive. In general, however, this struggle in nature is competition, not conflict. Social animals, such as monkeys and cattle, fight to win or maintain leadership of the group. The struggle for existence occurs not in such fights, but in the competition for limited feeding areas and for occupancy of areas free from meat-eating animals. Those who fail in this competition starve to death or become victims to other species. This struggle for existence does not resemble human war, but rather the competition of individuals for jobs, markets, and materials. The essence of the struggle is the competition for the necessities of life that are insufficient to satisfy all.

Among nations there is competition in developing resources, trades, skills, and a satisfactory way of life. The successful nations grow and prosper; the unsuccessful decline. While it is true that this competition may induce efforts to expand territory at the expense of others, and thus lead to conflict, it cannot be said that war-like conflict among nations is inevitable, although competition is.

The passage is probably intended to answer the question"()."

A. Is war inevitable

B. Why is there conflict and competition

C. Is conflict desirable

D. Can competition lead to conflict