Workers built shelters for s____ whose homes had been destroyed.
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合成氨是人类科学技术上的一项重大突破,其反应原理为:N2(g)+3H2(g)⇌2NH3(g),一种工业合成氨,进而合成尿素的简易流程图如下:
传说中,炎帝和黄帝是( )的部落联盟首领.