i为虚数单位，＝( )A．－1 B．1 C．－i D．i
某反应过程能量变化如图所示，下列说法错误的是 A．反应过程b有催化剂参与 B．该反应为放热反应，热效应等于△H C．改变催化剂，可
乙烯具有促进果实成熟的作用，还是合成纤维、橡胶、塑料的基本化工原料．乙烯无色，不溶于水，密度比空气小，化学式为C2H4，容易燃烧生成二氧化
豌豆、酪氨酸酶基因、RNA肿瘤病毒中参与构成核酸的碱基种类数，依次分别是 A 4 4 5 B 5 4 4 C 4 5 4 D 5 4 5
某运动员投篮命中率为，他重复投篮5次，若他命中一次得10分，没命中不得分，命中次数为，得分为，则分别为（ *** ） A．，60 B．3，1
．下列去括号正确的是（ ）A． ﹣（a+b﹣c）=﹣a+b﹣c B． ﹣2（a+b﹣3c）=﹣2a﹣2b+6cC． ﹣（﹣a﹣b﹣c）=﹣a+b+c D． ﹣（a﹣b﹣c）=﹣a+b﹣c
It was Saturday. As always, it was a busy one, for “Six days shall you labor and do all your work” was taken seriously back then. Outside, Father and Mr. Patrick next door were busy chopping fir
I wondered _____ they always looked down upon me. A. why it was which B. why it was that C. why was it that D. what was it that
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