问题 选择题

森林在调节大气成分中起重要作用,因为森林中的绿色植物通过光合作用,可以向自然界提供大量的(  )

A.二氧化碳

B.有机物

C.水

D.氧气

答案

绿色植物在光合作用中制造氧,超过了自身呼吸作用对氧的需要,其余的氧气都以气体形式排到了大气中;绿色植物还通过光合作用,不断消耗大气中的二氧化碳,这样就维持了生物圈中二氧化碳的氧气的相对平衡,简称碳-氧平衡.

    一个人一天平均吸入25千克空气,消耗其中约1千克氧. 当空气中的氧含量下降到7%~8%时,人就会昏迷、窒息、甚至死亡.有人曾做过这样的计算:1公顷树林的叶片的总面积约为50000~70000平方米,每天能吸收150~500千克的二氧化碳,放出60~400千克的氧气.可见绿色植物在维持碳-氧平衡方面的作用是多么重要.选D

故选:D

阅读理解

Is the world too crowded? Well, that’s a hard question to answer. It’s all a matter of perspective(视角).In Montana, you might drive for a mile in any direction and not see another human being. In Macao, 60,000 people live in every square mile!

What is true is that the world’s population doesn’t stay the same. It has been increasing at a very fast rate(比例).That’s in part because in each generation(代) these are more people who then have children than in the last generation.

Five hundred years ago, the population of the world was about 460 million. In 1900,the world’s population was under 2 billion(十亿).Right now it is doubling every 40 years. That means, if this rate of growth continues, when you are a parent, there will be twice as many people on earth as there are now. Wow! Now that’s a whole lot of people! Soon the world’s population will probably reach 7 billion. Some people worry about that! But there is a lot of disagreement about just how many people on earth equals(相当于) too many people. But everyone agrees that the more people there are, the more resources(资源) the world needs to feed, house and take care of all of them, and the more need there is to think carefully about how we live and use the earth’s resources.

小题1:From the first paragraph we can know that ­________.

A.Montana is too crowded

B.Macao is too crowded

C.the world is too crowded

D.the world is not too crowded小题2:The population is increasing fast partly because ________.

A.people live longer than before

B.there are less wars than before

C.medicine is developing faster than before

D.more couples now would like to have children than before小题3:What was the world’s population 100 years ago?

A.450 million.

B.about 2 billion.

C.40 billion.

D.7 billion.小题4:The writer thinks that with the population increasing, we should ________.

A.find more resources

B.use more resources

C.think about our ways of living

D.move to other places小题5:From the passage we can learn that the writer ________.

A.thinks the world already has too many people

B.thinks the world can feed no more than 7 billion people

C.is not sure when the world’s population will reach 7 billion

D.is not sure what the largest population that the world can feed is

单项选择题