问题 单项选择题

有些土壤学家声称森林地面的腐烂物比降在湖中的酸雨更会增加高山湖水酸性。因此,他们认为减少酸雨并不一定能明显地降低高山湖泊的酸性水平。 下面哪个论述,如果正确,最严重地削弱了上面的论点( )

A.高山湖泊的酸性比其他湖泊高是很正常的

B.人们严重低估了湖水酸性升高的危害

C.如果有植物生命存在,酸雨会显著增加自然环境中腐烂的有机物的数量

D.土壤学家对酸雨的成因意见分歧很大

答案

参考答案:C

解析: 题干指出造成高山湖水呈酸性的主要因素是森林腐烂物,因此得出结论:减少酸雨并不能降低高山湖水酸性。若C项所述为真,则证明酸雨虽然不会直接导致高山湖水酸化,但却可以促使高山湖水酸化的主要因素——森林腐烂物的增加,从而间接导致高山湖水酸化,因此也就说明减少酸雨能够有效降低高山湖水酸性水平,从而削弱了题干结论。A、B、D三项为无关项,均不能削弱题干结论。

单项选择题
单项选择题

Americans usually consider themselves a friendly people. Their friendships, however, tend to be shorter and more casual than friendships among people from other cultures. It is not uncommon for Americans to have only one close friend during their life-time, and consider other "friends" to be just social acquaintances. This attitude probably has something to do with American mobility and the fact that Americans do not like to be dependent on other people. They tend to "compartmentalize" friendships, having "friends at work" ,"friends on the softball team", "family friends", etc.

Because the United States is a highly active society, full of movement and change, people always seem to be on the go. In this highly charged atmosphere, Americans can sometimes seem brusque or impatient. They want to get to know you as quickly as possible and then move on to something else. Sometimes, early on, they will ask you questions that you may feel are very personal. No insult is intended; the questions usually grow out of their genuine interest or curiosity, and their impatience to get to the heart of the matter. And the same goes for you. If you do not understand certain American behavior or you want to know more about them, do not hesitate to ask them questions about themselves. Americans are usually eager to explain all about their country or anything "American" in which you may be interested. So much so in fact that you may become tired of listening. It doesn’t matter, because Americans tend to be uncomfortable with silence during a conversation. They would rather talk about the weather or the latest sports scores, for example, than deal with silence.

On the other hand, don’t expect Americans to be knowledgeable about international geography or world affairs, unless those subjects directly involve the United States. Because the United States is not surrounded by many other nations, some Americans tend to ignore the rest of the world.

Which of the following statements is NOT TRUE according to the passage()

A. Americans do not like to depend on other people

B. Friendships among Americans tend to be casual

C. Americans know a lot about international affairs

D. Americans always seem to be on the go