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问题 选择题

下面关于“2”涵义的解释中，正确的是（　　）

A．CH2O中的“2”表示一个甲醛分子中含有2个氢离子

B．3H2SO4中的“2”表示3个硫酸分子中含有2个氢原子

C．Ca2+中的“2”表示一个钙离子带2个单位电荷

D．Al2（SO4）3中的“2”表示3个硫酸根的化合价为-2价

答案

A、CH2O中的“2”表示一个甲醛分子中含有2个原子，故A错误；

B、3H2SO4中的“2”表示1个硫酸分子中含有2个氢原子，故B错误；

C、Ca2+中的“2”表示一个钙离子带2个单位的正电荷，故C正确；

D、Al2（SO4）3中的“2”表示一个Al2（SO4）3含中2个Al3+，故D错误；

故选：C．

完形填空

The private automobile has long played an important role in the US. In fact, it has become 小题1:___necessary and important part of the American life. In 1986, sixty-nine percent of American families owned 小题2:__least one car, and thirty-eight percent had 小题3:___than one. With the convenience of rapid transportation, workers don’t have to live near their workplace. This has encouraged the growth of the cities, 小题4:___it has also led to traffic problems.

For farm families the automobile is very helpful. It has made 小题5:___ possible for them to travel to town very often for business and for pleasure.

Family life has been affected in 小题6:___ways. The car helps to keep families together. However, when teenage children use the car, their parents can’t keep an eye on them. There is a great danger 小题7:____the driver has been drinking alcohol or taking drugs or breaking 小题8:_____ traffic laws.

Cars mean very much to Americans.
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单项选择题

鉴别再障和急性白血病的最主要的检查项目是

A．血小板数

B．周围血查幼粒细胞

C．骨髓检查

D．周围血查幼红细胞

E．网织红细胞数
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