下列气体中，只能用排水集气法收集的是（ ） A.H2 B.NO C.NO2 D.CO2
阅读短文,简要回答下面的问题。 Wang was born into a rich family in America, but he was not a spoiled child． His parents made him practice violin for hours every day and he
A teacher's________to the cause of education is worth great respect of the whole society because it brings countless benefits to the development of society. A．devotion B．principle
在△中,sin, 则cos等于( ) A、 B、 C、 D、
What a table! I’ve never seen such a thing before. It is _____ it is long. A. half not as wide as B. wide not as half as C. not half as wide as D. as wi
483g Na2SO4·10H2O中所含的Na+的物质的量是 和SO42—的物质的量是 ，所含H2O分子的数目是 个。
下列有关物质的分类正确的是 A．石油、煤、小苏打都是混合物 B．烧碱、纯碱、碱石灰都是碱 C．HNO3、NaOH、NaNO3都是电解质 D．HCl、H2SO
When Robinson Crusoe got to the island，the first thing __ __ he did was to look for some food. A．who B．that C．which D．whom
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