某同学将一小块金属钠和一块铁片分别放在表面皿中，研究它们在空

某同学将一小块金属钠和一块铁片分别放在表面皿中，研究它们在空气中的稳定性。该学生采用的研究方法是： ①假说法 ②实验法 ③分类法 ④比较法

A．① ② B．① ③ C．② ④ D． ② ③

答案

解析:

相关题目

若⊙O的半径为5cm，点A到圆心O的距离为4cm，那么点A与⊙O的位

若⊙O的半径为5cm，点A到圆心O的距离为4cm，那么点A与⊙O的位置关系是A. 点A在圆外 B.点A在圆上C. 点A在圆内 �

This was returned because the person _____ this letter was addressed had died th

This was returned because the person _____ this letter was addressed had died three years ago． A． to whom B． to which C． which D． whom

（08江苏卷）某植物种群中，AA个体占16%，aa个体占36%，该种

（08江苏卷）某植物种群中，AA个体占16%，aa个体占36%，该种群随机交配产生的后代中AA个体百分比、A基因频率和自交产生的后代中AA个体百分比、A基因

His parents, ，did not look after him very well: the elbows of his jacket a

His parents, ，did not look after him very well: the elbows of his jacket and his boots were badly worn. A. generally B. gradually C. actively D. apparently

— does this umbrella belong to? —I think it must

— does this umbrella belong to? —I think it must be . A. whom; hers B. whom; her C. w

砷的一些化合物常用作半导体、除草剂、杀鼠药等。回答下

砷的一些化合物常用作半导体、除草剂、杀鼠药等。回答下列问题： (1)基态As原子的核外电子排布式为[Ar]__________，有___________个未成对电子。 (2)镓氮砷

欲配制100 mL 1.0 mol/L Na2SO4溶液，正确的方法是（）① 将1

欲配制100 mL 1.0 mol/L Na2SO4溶液，正确的方法是（）① 将14.2 g Na2SO4 溶于100 mL水中② 将32.2 g Na2SO4·10H2O溶于少量水中，再用水稀释至100 mL③ 将20 mL 5.0

—Did you receive my letter? —I received one just as I .

—Did you receive my letter? —I received one just as I . A．set out B．had set out C．was setting out D．would set out

某同学将一小块金属钠和一块铁片分别放在表面皿中，研究它们在空

答案

相关题目

最新题目