问题 单项选择题

 原始地球形成后的八亿年,其内部逐渐变热使局部熔融并超过铁的熔点,其使地球中的金属铁、镍及硫化铁熔化,并因密度大而流向地球的中心部位,从而形成液态铁质地核。同时,地球的平均温度进一步上升(可达约2 000摄氏度),引起地球内部大部分物质熔融,比母质轻的熔融物质向上浮动,把热带到地表,经冷却后又向下沉没。这种对流作用控制下的物质移动,使原始地球产生全球性的分异,演化成分层的地球,即中心为铁质地核,表层为低熔点的较轻物质组成的最原始的陆核,陆核进一步增生,扩大形成地壳。地核与地壳之间为地幔。分异作用是地球内部最重要的作用,它导致了地壳及大陆的形成,并导致大气和海洋的形成。所以说,我们的地球是原始地球再生的,这个再生过程大约发生在40亿年前(或说37亿年前至45亿年前之间),即我们已经发现的最古老岩石的形成时期之前氢和氧合成的水,原先潜藏于一些矿物中。当原始地球变热并部分熔融时,水释放出来并随熔岩运移到地表,人部分以蒸气状态逸散,其余部分在漫长的地质历史进程中逐渐充满大洋。在原始地球变热而产生分异作用的过程中,从地球内部释放出来的气体形成了大气圈。早期地球的大气圈成分与现代不同,正是由于紫外辐射的能量促使原始大气成分之间发生反应,从无机物质生成有机小分子,然后发展成有机高分子物质组成的多分子体系,再演变成细胞,生命得以开始和进化。

不属于“分异作用”的一项是()。

A.金属铁、镍及硫化铁熔化,并因密度大流向地球中心部位

B.比母质轻的熔融物质向上浮动

C.无机物质生成有机小分子

D.陆核进一步增生,扩大形成地壳

答案

参考答案:C

阅读理解

阅读理解。

     In Africa I heard a story about a giraffe that did not believe himself.

     The giraffe's mother had left him when he was a few days old because she couldn't feed

him. For three years he lived in the warden's 看守人) house and played with the children. Then he grew

too large for the house.

     The family decided that he should return to his fellows. They took him to join a herd of wild giraffes.

     One look was enough for the giraffe's small brain. He could not believe that such extraordinary(特别的) animals existed. Or that he was one of them ! He turned and ran away.

    The family took him back several times. In the end they gave up. Now their giraffe lives by himself near

the warden's house.

1. The baby giraffe was probably separated from his mother because _______.

A. the warden took him away

B. his mother couldn't feed him

C. the warden's children took him

D. he ran away

2. After three years the giraffe became_______.

A. too wild to play with the children

B. too large to play with the children

C. popular with other giraffes

D. too big to live in the house

3. The warden's family tried to_______.

A. Let the giraffe do what he liked

B. find the giraffe's mother

C. tell the giraffe what he was

D. take the giraffe to join the herd of wild giraffes .

4. When he met the herd, the giraffe could not understand _______.

A. how animals like giraffes could exist

B. why he wouldn't join the other giraffes

C. that he was really a giraffe, too

D. both A and C

5. The story suggests that _______.

A. most mother giraffes leave their babies

B. giraffes are too large to be pets forever

C. giraffes are not very smart

D. this giraffe was unusually tall

单项选择题