皮带机头至少应配备（）个灭火器。A.1 B.2 C.3

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问题单项选择题

皮带机头至少应配备（）个灭火器。

A.1

B.2

C.3

答案

参考答案：B

选择题

_____ a written permission, he had to write another letter to the president of the university. [ ]

A. Not giving

B. Not having been given

C. Having not given

D. Having not been given

不定项选择题

以下自发反应能用ΔH判据来解释的是[ ]

A．硝酸铵自发地溶于水

B．2N₂O₅(g)＝4NO₂(g)＋O₂(g)　ΔH＝＋156.7 kJ·mol^-1

C．(NH₄)₂CO₃(s)＝NH₄HCO₃(s)＋NH₃(g)　ΔH＝＋74.9kJ·mol^-1

D．2H₂(g)＋O₂(g)＝2H₂O(l)　ΔH＝－285.8 kJ·mol^-1