Answer:
The correct answer is 2. The U.S. president that became the first to ever visit China, setting off a period of detente, was Richard Nixon in 1972.
Step-by-step explanation:
The visit of President Richard Nixon to the People's Republic of China was an important step to formally normalize relations between the United States and the People's Republic of China. It was the first time that a president of the United States visited the PRC, which at that time considered the United States as one of its most important enemies. Among the American public, the visit became a metaphor for an unexpected or uncharacteristic action of a politician.