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【单选题】
地球的外围是一层很厚的大气层，厚度大约在1000千米以上，但没有明显的界线。整个大气层随高度不同表现出不同的特点，分为对流层、平流层、中间层、电离层和散逸层。下列关于各层次大气层的说法正确的是（）A.
中间层基本上没有水汽，晴朗无云，很少发生天气变化，适于飞机航行
B.
许多有趣的天文现象，如极光、流星等经常发生在电离层
C.
云、雨、雪、雹等主要的天气现象发生在对流层
D.
只有地球有电离层，金星、火星和木星都没有电离层
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【简答题】Today a new generation of sociologists continues to further study the puzzle of ______.
【单选题】According to Paragraph 2, a new study finds that______.
A.
learning a new language can benefit a lot when you grow old
B.
you have to learn a new language at a very young age
C.
picking up a new language have few benefits later in life
D.
picking up a new language can cause serious health problems
【多选题】已知由同种元素组成的不同种单质，互称为同素异形体。例如金刚石和石墨是同素异形体，红磷和白磷也是同素异形体。某同学查阅有关资料得知：铁有δ-Fe、γ-Fe、α-Fe三种同素异形体。三种晶体在不同温度下能发生以下转化。下列有关说法正确的是 [ ]
A.
构成它们的原子大小不同
B.
δ-Fe、γ-Fe、α-Fe之间的相互转化是化学变化。
C.
δ-Fe、γ-Fe、α-Fe一定由不同种类的铁原子构成
D.
δ-Fe、γ-Fe、α-Fe里铁原子的排列不同
【单选题】( ) is the study of the various aspects of the relation between language on the one hand and speakers and society on the other.
A.
Pragmatics
B.
Sociolinguistics
C.
Syntax
D.
Semantics
【简答题】A new study shows a relationship between fast walking and life expectancy. For this study, researchers looked at walking speed and other health factors for almost 35,000 older s. They followed th...
【简答题】Having a child may improve a woman’s memory, a new study suggests. In the study, women who were new mothers scored better on tests of visuospatial memory – the ability to understand and remember infor...
【简答题】Moving to a new town or even a new neighborhood is stressful at any age, but a new study shows that frequent moves in childhood are related to poorer well-being(幸福) in hood, especially among peop...
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