问题 选择题

人们大量捕杀麻雀,将导致生态系统的稳定性被破坏,其主要原因是:(   )

A.破坏了植被

B.破坏了食物链

C.污染了环境

D.杀灭了物种

答案

答案:B

麻雀以生态系统中的一些昆虫为食,如果大量捕杀麻雀,昆虫就会因为失去天敌而大量繁殖,食物链遭到了破坏,那么生态系统的稳定性就会被破坏。

单项选择题
单项选择题

"In the long run," as John Maynard Keynes observed, "we are all dead. " True. But can the (1) run be elongated in a way that makes the long run (2) And if so, how, and at what cost People have dreamt of (3) since time immemorial. They have sought it since the first alchemist put an elixir of (4) on the same shopping list as a way to turn lead into gold. They have (5) about it in fiction, from Rider Haggard’s "She" to Frank Herbert’s "Dune". And now, with the growth of (6) knowledge that has marked the past few decades, a few researchers believe it might be within (7) .

To think about the question, it is important to understand why organisms-people (8) -age in the first place. People are like machines: they (9) That much is obvious. However, a machine can always be (10) A good mechanic with a stock of spare parts can keep it going (11) . Eventually, no part of the (12) may remain, but it still carries on, like Lincoln’s famous axe that had three new handles and two new blade.

The question, of course, is whether the machine is worth (13) . It is here that people and nature (14) . Or, to put it slightly (15) , two bits of nature disagree with each other. From the individual’s point of view, (16) is an imperative. You cannot reproduce unless you are alive. A fear of death is a sensible evolved response and, since (17) is a sure way of dying, it is no surprise that people want to stop it in its tracks. Moreover, even the appearance of ageing can be (18) . It (19) the range of potential sexual partners who find you attractive-since it is a sign that you are not going to be (20) all that long to help bring up baby-and thus, again, curbs your reproduction.

14()

A.compromise

B.agree

C.disagree

D.consent