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问题 选择题

某学生的实验报告有如下数据：①用托盘天平称取11.7g食盐；②用量筒量取21.48mL盐酸；③用容量瓶配制210mL1mol/L的硫酸溶液；④用标准NaOH溶液滴定未知浓度的盐酸，用去18.20mLNaOH溶液，其中数据合理的是（　　）

A．①④

B．②④

C．①③

D．②③

答案

①托盘天平称量物质准确度为0.1g，可称取11.7g食盐，故①正确；

②量筒量取液体体积的准确度为0.1mL，所以量取21.48mL不合理，故②错误；

③容量瓶的规格中有50mL、100mL、200mL、250mL、500m、1000mL等等，没有210mL的，故③错误；

④中和滴定要用滴定管，滴定管的准确度为0.01mL，18.20mL的数值合理，故④正确；

故选A．

单项选择题

下列关于栈的描述中错误的是______。

A．栈是先进后出的线性表

B．栈只能顺序存储

C．栈具有记忆作用

D．对栈的插入与删除操作中，不需要改变栈底指针
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单项选择题

The development of e-commerce may well bring the world into a brand new era of "electronic currency". At the moment, (51) areas in Europe, the United States and Asia have already started studying the possibility of an electronic currency. Electronic currency is not only about currency. It (52) to an entire finance system on the Net. It includes a virtual numeric currency, an electronic system of withdrawals, transfers and loans, and (53) cards of all shapes and sizes. The (54) of an electronic currency system implies the emergence of "virtual banks" and "virtual enterprises". Actually, the first virtual bank appeared in the US in 1995. (55) it is a small and insignificant bank, it represents the trend of the future. In time to come, we may even have to (56) the familiar paper currency.

As the Net pushes the economy (57) rapidly, the economy is also bringing the Net market forward, resulting in the Internet itself becoming the world’s largest emerging market. Of course, this is just the beginning. Although there are many companies which made huge profits (58) in the Internet market, they tend to be small companies. To date, most companies are making losses. The competition in the knowledge-based economy will also be more (59) This will definitely promote (60) and more efficient cooperation.

52().

A.bridges 

B.camps 

C.refers 

D.casts
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