关于挫折和创新的关系，下列说法正确的是 （    ）
①人类文明在不断创新中完善                                         ②挫折激励创新，创新战胜
③克服困难和挫折，需要开拓进取，勇于创新             ④创新是民族进步的灵魂，是国家兴旺发达的不竭动力 

阅读下面短文，然后从所给的四个选项中选出一个最佳答案。

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①国家的主权不容侵犯                   ②主权等国家利益关系到民族生存、国家兴亡

③维护国家统一是政府的事           ④美国是一个霸权国家，我们要坚定维护国家利益

电动机正常工作时，将电能转化为人们需要的____ 能。