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问题 选择题

设NA代表阿伏加德罗常数，下列说法正确的是                   

A．标准状况下，5.6L四氯化碳含有的分子数为0.25NA

B．2.4g金属镁变为镁离子时失去的电子数为0.2NA

C．H2SO4的摩尔质量是98 g/mol

D．物质的量浓度为0.5mol/L的MgCl2溶液中，含有Cl-个数为1 NA

答案

BC

填空题

watch    learn     be    have      Chinese    

Dick and Ellen come from America. Now they 81_____________ in Tianjin. Every morning they get up very early. Then they go to work by car. They start their work at 8:30. They are very busy. They 82_____________ lunch at 12:30. After lunch they work again. They finish their work at 5:30 p.m. In the evening Dick takes Chinese lessons because he wants 83______________ Chinese. Ellen stays at home and 84____________ TV. They like to talk with Chinese people. They often say "Chinese people are very friendly". They like to stay in 85______________ and they like to work with Chinese people.

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单项选择题

下面的描述是有关竹柏属的特征的是（）。

A.叶背有两条气孔带

B.果实为荚果

C.无明显中脉

D.叶扇形
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