题目内容：

阅读材料，回答问题。  

材料一  “战国”因战争频繁、争夺激烈而得名。战国时期是我国古代史上一个战火纷飞、色彩斑斓的时代……                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                                    

（1）依据材料一，指出战国时期最显著的特点是什么？结合所学知识，简要指出此时的战争在客观上有哪些积极的作用？

材料二  秦始皇在咸阳宫举行的一次庆功宴上对群臣说：“天下共苦，战斗不休，以有诸侯”。

——《史记•秦始皇本纪》

（2）根据材料二，指出秦始皇认为“天下战争不断”的根源是什么？为此，秦始皇实行什么政治制度来管理地方？

材料三  中国古代的中央集权制度，从产生之日起，其组织机构就具有多民族、大一统的性质，其职能就具有维护、推动、发展和形成多民族、大一统国家的历史任务。

                                                                 ——凤凰网

（3）依据材料三，概括中央集权制度对我国历史发展的积极作用。