The answer is. <span>A)It prevented European countries from taking advantage of China's resources. At that time, China was in a dire state following their war with the Japanese. The open-door policy created by John Hay's was established to make United States able to maintain equal footing to obtain trading relationships with China so it's not fully controlled by the European nations.</span>
The name of the agreement that took place from 1968 to 1973 wherein negotiations between the USA and Vietnam led to a ceasefire was the Paris Peace Accords. The agreement led to the end of the Vietnam War between the northern communist Vietnam against the southern democratic Vietnam.