The united states government agreed to become involved in the korean and vietnam wars
a. they wanted to create stable economies in southeast asian countries in order to promote trade
b. war in those countries threatened japan, which had a very fragile post-war democracy
c. many believed the u. s. should take an active hand in stopping the spread of communism
d. as a member of nato, the u. s. was required to protect its allies in the organization

C.many believed the U.S. should take an active hand in stopping the spread of communism

Explanation:

As the biggest and main leader of the capitalist hemisphere of the world, USA´s role after WWII was to fight the communist efforts to create and expand their influence on the globe, the wars on Vietnam and Korea were mainly the physical repercution of the cold war, USSR was founding the efforts of one side on both wars, while USA was actively fighting both wars helping the other side.

the triple alliance. germany and austria-hungary were already allies by 1879 when, worried about a threat from russia, they formed the dual alliance. italy joined the group in 1882. there was a concern about a possible attack from france and the alliance needed powerful friends to defend it.