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How to Get Preserved as a Fossil 【71】Unfortunately the chances of any animal become a fossil are not very great, and【72】the chances of a fossil then being discovered many thousand of years later are even less.【73】It is not surprising that all the millions of animals that have lived in the past【74】we actually have fossils of only very few. 【75】There are several ways into which, animals and plants may become fossilized.【76】First, it is essential that the remains are buried, as though dead animals and plants are quickly destroyed【77】if they remain exposed the air. Plants rot, while insects and hyenas eat the flesh and bones of animals. 【78】Finally, the few remaining bones soon disintegrate the hot sun and pouring rain. If buried in suitable conditions, however, animal and plant remains will be preserved. 【79】The same chemicals change sand and silt into hard rock will aim enter the animal and plant remains and make them hard too.【80】When this happens, we say that they become fossilized. (71)
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举一反三
【单选题】关于个性,下列哪种叙述是错的()
A.
个性的形成与先天遗传因素和后天环境因素都有关系
B.
个性是个体心理特征的总和
C.
个性一旦形成就不会改变
D.
童年生活经历对个性形成有重要作用
【单选题】中国的音乐节是什么时候?
A.
四月五日
B.
五月四日
C.
六月六日
D.
七夕
E.
十二月二日
【简答题】先天因素和后天因素的关系?
【单选题】若土工试验测得土的孔隙率大于1.0,说明土的状态是( )。
A.
疏松土
B.
密实土
C.
压实土
D.
膨润土
【单选题】如图所示,刚体受三力作用,并且三力均不为零,则 。
A.
情况(a)刚体不可能平衡
B.
情况(b)刚体不可能平衡
C.
两种情况都不可能平衡
D.
两种情况都可能平衡
【判断题】领导者的素质与一定先天的生理素质有关系,但决定因素是后天社会实践的培养和训练。()
A.
正确
B.
错误
【单选题】世界上第一个网络诞生于
A.
1946 年
B.
1969 年
C.
1977年
D.
1973 年
【判断题】当某区间发生阻塞时,隧道通风系统将按与行车相反的方向进行纵向通风。
A.
正确
B.
错误
【单选题】下面哪一个字母表示自然数集
A.
R
B.
N
C.
Z
D.
Q
【单选题】如图所示,刚体受三力作用,并且三力均不为零,则
A.
情况 a 刚体不可能平衡
B.
情况 b 刚体不可能平衡
C.
两种情况都不能平衡
D.
两种情况都可能平衡
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