Why did Richard Nixon want to improve relations with China?

Improved relations with the Soviet Union and the PRC are often cited as the most successful diplomatic achievements of Nixon's presidency. ... The reason for opening up China was for the U.S. to gain more leverage over relations with the Soviet Union. Resolving the Vietnam War was a particularly important factor.

option d is correct. corroborated sources of historical evidence   is necessary to validate a claim about an event in history.

historians tend to use written sources, but audio and visual materials as well as artifacts are important objects that supply information to modern historians.

historical sources are usually divided into two categories: primary and secondary sources. depending on the historian's intent, some sources shift their designation. determining what type of sources toimplement, and the level of credibility and reliability of those sources, is a significant step in critical thinking for the historian.

explanation:

map scale refers to the relationship (or ratio) between distance on a map and the corresponding distance on the ground. for example, on a 1: 100000 scale map, 1cm on the map equals 1km on the ground.