单项选择题

The maximum diameter of a certain ore is 30mm. If K=0.05 and a=2, the amount of sample should be taken as ( )

A．1.5g
B．1.5kg
C．45kg
D．Not less than the amount of analysis

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单项选择题

( )占了澳大利亚国家土地面积的约60%。

A．山地
B．沙漠与草原
C．平原
D．丘陵地区

单项选择题

Which of the following is NOT true about Tartar Pipe? A、Tartar Pipe is a reed wind instrument, also named clarinet. B、It first appeared in the Qing Dynasties. C、It had been widely used by the folk in the Western Han Dynasty. D、It was introduced from the West Asia or India into Central Asia.