The correct answer is B) they worried that Communism would spread from China to other countries in Eastern and South East Asia.
United States Officials reacted to the Communist winning the Chinese Civil War in that they worried that Communism would spread from China to other countries in Eastern and South East Asia.
Mao Zedong was the leader of the Communists in China. On October 1, 1949, he created the People's Republic of China. With this announcement, the Civil War had officially ended, Mao Zedong troops defeated the Nationalist Party army. After the victory of Zedong and the implementation of Communism in China, the United States suspended diplomatic relationship with China. So yes, United States Officials reacted to the Communist winning the Chinese Civil War in that they worried that Communism would spread from China to other countries in Eastern and South East Asia.