The correct answer is B. The United States supported Ngo Dinh Diem because he was anti-Communist.
Ngo Dinh Diem was a Vietnamese politician and a central figure at the beginning of the Vietnam War, remembered for his role in establishing the Republic of Vietnam (South Vietnam), being its first president (1955-1963).
Diem obtained a lot of support at the beginning of his government by the United States, as one of his values was his anti-communist history. However, his relations with the American government deteriorated over time.
