题干

我国谚语中的“螳螂捕蝉,黄雀在后”体现了食物链的原理.若鹰迁入了蝉,螳螂和黄雀所在的树林中,捕食黄雀并在栖息于林中,下列叙述正确的是(  )

A:鹰的迁入增加了该树林中蝉及其天敌的数量

B:该生态系统中细菌产生的能量可流向生产者

C:鹰的迁入增加了该生态系统能量消耗的环节

D:鹰的迁入改变了该生态系统能量流动的方向

上一题 下一题 0.0难度 选择题 更新时间:2013-01-11 04:39:40

答案(点此获取答案解析)

C

同类题3

阅读下面短文,从短文后所给的五个选项中选出能填入短文空白处的最佳选项,使短文通顺、连贯,意思完整。

Teenage life—better now, or in the past?

    Does this situation sound familiar(熟悉)?

    You are complaining(抱怨)to your parents about something. Maybe your computer isn't powerful enough to play the latest games.____.Then you hear…

    “When I was your age, there weren't any computers or video games. And I didn't get a bike until I was sixteen. And it was second-hand.____

    So, is it really true that life is better for teenagers now? It is certainly true that many teenagers have got more things nowadays.____So parents have got more money to spend on each child. And many things are cheaper than they were when our parents were children.

    ____ Forty years ago, no one could imagine a world with tiny computers and amazing smartphones. And now these things are necessary—we can't imagine living without them!

    However, technology often means we spend more time at home. And often it's just us, with our computer or television. Teenagers don't do enough exercise.____ And, although young people still get on well with their friends, some people think teenagers today don't have so many social activities as they did in the past.

    What do you think? How is teenage life better these days?

A. And it was too big for me.

B. A typical family is smaller now.

C. Or your friends' bikes are better than yours.

D. So they aren't as healthy as they were in the past.

E. Technology is probably the greatest change in our life.