美中三公報 臺灣關係法 六項保證 一中政策 策略模糊 戰略伙伴關係 三不政策 三個支柱 和平解決 臺灣人民的同意 The three US-PRC communique's Taiwan relations act Six assurances One China policy Strategic ambiguity Constructive strategic partnership Three noes Three pillars Peaceful resolution The assent of the Taiwanese