The United States involved itself in Vietnam in the 1960s because:

A. The American people demanded the government support Vietnam

B. American Businesses in Vietnam were threatened by the communist

C. It feared that if Vietnam became communist then surrounding countries would quickly follow it feared that is Vietnam became communist then surrounding countries would quickly follow.

D. Japan was threatened militarily by the possibility of a communist government in Vietnam.
.

C. It feared that if Vietnam became communist then surrounding countries would quickly follow it feared that is Vietnam became communist then surrounding countries would quickly follow.