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问题 多项选择题

在火场上，当灭火力量优于火势发展时，灭火战斗行动是主动的，此时应在控制火势的过程中()消灭火灾。

A、积极

B、主动

C、适时

D、逐步

E、及时

答案

参考答案：A, B, E

选择题

They _______ on the program for almost one week before I joined them,and now we _______ it as no good results have come out so far.

A．had been working; are still working

B．had worked; were still working

C．have been working; have worked

D．have worked; are still working
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选择题

用Cl2生产某些含氯有机物时会产生副产物HCl。  利用反应A：4HCl＋O2 2Cl2＋2H2O，  

可实现氯的循环利用。

已知：Ⅰ．反应A中，4mol HCl被氧化，放出115．6kJ的热量．

Ⅱ．则断开1 mol H—O键与断开1 mol H—Cl键所需能量相差约为

A．16kJ

B．24kJ

C．32kJ

D．48kJ
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