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问题 读图填空题

人体的发育起始于_________。

答案

受精卵

人体的生长发育是从受精卵形成胚胎并且长成为性成熟个体的过程．人体的发育包括两个过程，一是从受精卵发育到成熟的胎儿的胚胎发育阶段；二是从婴儿出生发育到个体成熟的胚后发育阶段．卵细胞不能进行细胞分裂、分化、发育等生命活动．只有精子与卵细胞结合形成受精卵时，才是人体发育的起点．受精卵经过细胞分裂、分化，形成组织、器官、系统，进而形成胎儿．

故答案为：受精卵

单项选择题

在工业生产中，为满足生产工艺的要求，常常需将固体原料、产品进行筛选，以选取符合工艺要求的粒度，这一操作过程称为( )。

A．过滤

B．筛分

C．分层

D．蒸馏
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完形填空

课文填空。以下是两篇课文选段，请任意选择一篇，并根据课文，在文中划线处填上适当单词，每空一词， (共10小题，计10分) 

1). Some festivals are held to honour the dead or to ___1_____ the ancestors, who might return _____2__ to help or to do ____3____. For the Japanese festival Obon, people should go to clean graves and light incense in ____4____ of their ancestors. They also light lamps and play music because they think this will __5_____ the ancestors back to earth. In Mexico, people celebrate the Day of the Dead in early November. _6____ this important feast day, people eat food in the _7____ of skulls and cakes with “ bones” on them. They offer food, flowers and gifts to the dead. The Western holiday Halloween also had its ___8______in old _____9_ about the return of the spirits of dead people. It is now a children’s festival, when they can dress up and go to their neighbours’ homes to ask for sweets. If neighbours do not give any sweets, the children might play a __10____ on them.

2)       According to a widely ____1___ theory, the universe began _____2__ a “Big Bang” that threw matter in all _____3____. After the “Big Bang”, the earth was still just a cloud of dust. ___4____ it was to become was uncertain until between 4.5 and 3.8 billion years ago when the dust _____5___ into a solid _____6__. The earth became so _____7___ that it was not clear ____8_____ the shape would last or not. It ____9______ loudly with fire and rock. They were in time to produce carbon, nitrogen, water vapour and other gases, which were to make the earth’s ___10______.
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