问题 选择题

大约40亿年前,地球还是炽热状态,陨石撞击导致地球失去了大部分的原始大气.原始大气中没有的气体是(  )

A.水蒸气

B.甲烷

C.氢气

D.氧气

答案

地质学家研究表明,地球大约是在46亿年以前形成的,那时候地球的温度很高,地面上的环境与现在的完全不同:天空中或赤日炎炎,或电闪雷鸣,地面上火山喷发,熔岩横流.从火山中喷出的气体,如水蒸气、氢气、氨、甲烷、二氧化碳、硫化氢等构成了原始的大气层,还有一部分硫化氢和氰化氢,虽有少量的水蒸气受到强烈的紫外线的作用,分解为氢和氧,但是氢由于太轻而浮到大气层的最高处,大部分逐渐消失在宇宙空间,而氧气很快与地面上的一些物质结合为氧化物,因此原始大气中没有氧气.

故选:D

多项选择题
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     Half an hour of exercise a day can add an extra five years on your life, a ground breaking research has

revealed.Health experts said that walking or cycling gently has massive longterm benefits.According to the World Health Organization, research carried out in Britain and Denmark shows that gentle workouts

(锻炼) and even housework every day can boost life spans by as much as five years.

      The news will provide encouragement for those couch_potatoes to start taking exercise.Britain is in

the grip of an obesity epidemic (肥胖症), with just 35% of men and 24% of women taking regular

exercise.

     "Encouraging people to be physically active every day has so many health benefits, " said Dr.Marc

Danzon, WHO regional director for Europe."These include reducing the risk of developing certain

diseases and of becoming obese, as well as contributing to physical coordination, balance, strength and

mental wellbeing.It is a very costeffective public health tool."

     The organization is so concerned that the public is not getting the message on exercise that it will 

 launch a "Move for Health" campaign to boost public awareness.

      "The WHO encourages adults to take at least 30 minutes of moderate physical exercise a day,

defined as any body movement that results in energy expenditure (消耗), " said Dr  Danzon."This

includes walking, cycling, playing, housework, climbing stairs as well as sports." He added that children

should take at least 60 minutes of exercise every day.

1. The underlined phrase "couch potatoes" probably means______.

A. lazy bones who spend a lot of time sitting

B. people who like eating potatoes

C. persons who usually rest on a couch

D. players who take exercise with potatoes

2. Taking physical exercise every day benefits one's health in the following aspects except________.

A. strengthening body coordination

B. developing certain diseases and becoming obese

C. keeping body balance

D. keeping fit mentally

3. Which statement is NOT true according to the passage?

A. Children should take more physical exercise than adults every day.

B. The WHO has tried to improve people's knowledge about exercise by launching a campaign.

C. People with an obesity epidemic in Britain seldom take regular exercise.

D. Physical exercise brings the best possible profit to public health at the lowest cost.

4. The passage mainly tells us________.

A. how to take exercise  

B. what the WHO is

C. how to lose weight  

D. how to add years to your life