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【单选题】
下列关于碱金属某些性质的排列中，正确的是A.
原子半径：Li＜Na＜K＜Rb＜Cs
B.
密度：Li＜Na＜K＜Rb＜Cs
C.
熔点、沸点：Li＜Na＜K＜Rb＜Cs
D.
还原性：Li＞Na＞K＞Rb＞Cs
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举一反三
【单选题】在换热器中,间壁任一侧的对流传热速率 = 推动力 / 阻力,其中推动力是指
A.
两相流体温度差（ T – T ˊ） ;
B.
冷流体进出口温度差（ T 2 ˊ -T 1 ˊ ） ;
C.
热流体进出口温度差（ T 2 -T 1 ） ;
D.
流体主体温度和管壁温度差（ T – T W ）或（ T W ˊ – T ˊ）
【简答题】某种产品的产量与单位在成本的资料如下： 产量(千件)x 单位成本(元/件)y 2 73 3 72 4 71 3 73 4 69 5 68 要求： (1)建立直线回归方程。 (2)指出产量每增加1000件时，单位成本平均下降了多少元? (3)假设产量为6000件时，单位成本为多少元？单位成本为70元时，产品应为多少件？
【单选题】Why did the author want to conceal the fact that he had seen the present?
A.
Because he did not think the present wonderful
B.
Because he didn’t want his sister to know that only he would have such a present
C.
Because he was not sure whether the present was for him
D.
Because he didn’t want to strike a blow against her mother’s happiness
【简答题】News Report 1. What inspired Mr. Lee to set up a translation company? A. The fact that he speaks more than six languages. B. The fact that some companies need translators. C. The fact that he once pro...
【简答题】If a free society cannot help the many who are poor,it cannot save the few who are rich.
【简答题】A．They cannot sit still or control their actions. B．They cannot talk fluently. C．They cannot study well. D．They cannot express their ideas well.
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