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问题 选择题

下列物质中既能与盐酸反应,又能与NaOH溶液反应的是[ ]

 ①Na2SiO3；②Al(OH)3；③NH4HCO3；④Al2O3

A.①②④

B.②③④　

C.②④

D.全部

答案

答案：B

选择题
A 7-year-old boy received an operation on Tuesday successfully _______ he has many other health problems.
A．since B．however
C．thoughD．therefore
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单项选择题

IEEE 802.11标准定义了______。

A．无线局域网技术规范

B．电缆调制解调器技术规范

C．光纤局域网技术规范

D．宽带网络技术规范
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