材料：2009年是建国60周年。60年前，毛泽东主席向全世界宣布：中华人民共和国成立了！从此，中国人民站了起来，当家做了主人，坚持走自己的路，取得了累累硕果，树立了和平、合作、负责任的国际形象。
（1）新中国成立后，我国的国家性质是什么？我国实行什么政治制度确保人民当家作主？
                                                                                                                                                                
                                                                                                                                                               
（2）在我国，一切权力属于人民。我国人民是通过什么方式行使权力的？
                                                                                                                                                               
                                                                                                                                                              
                                                                                                                                                               
                                                                                                                                                               
（3）请你举出实例，说明我国在国际社会中是和平、合作、负责任的国家。