Which of the following best explains why the United States went to war in Vietnam?
A. Lyndon Johnson believed that he needed to differentiate himself
from John F. Kennedy to win reelection.

B. Vietnam controlled access to valuable natural resources that
American corporations hoped to acquire.

C. Vietnamese communists refused to participate in open elections
to determine the country's postcolonial leadership.

D. U. S. foreign policy was rooted in the idea that the spread of
communism must be contained.