Final answer:
The Cold War and the fear of communism were crucial factors that led to the United States becoming involved in the Vietnam War.
Step-by-step explanation:
The correct answer is D. It raised officials' alarm about the global spread of communism. The Cold War between the United States and the Soviet Union was a key factor in the United States getting involved in the Vietnam War. The United States feared that if Vietnam fell to communism, it could lead to the spread of communism throughout Southeast Asia. This fear of the global spread of communism was a significant reason for the United States increasing its involvement in the Vietnam War.
Learn more about Cold War's role in the United States' involvement in the Vietnam War