Answer: The Shanghai Communiqué
Explanation:
The Shanghai Communiqué, signed in 1972, was a joint document between China and the United States during the Nixon administration, who was also the first president to visit China due to negotiations and discussions over this document. This document communicated these three ideas:
With this document, Taiwan was also considered a province of China, unifying the China into, geographically, one nation. The document still forms the basis of the US relations with China today.