What strategy did the United States adopt in Vietnam based on "domino theory"?

The United States committed millions of troops to the conflict in Vietnam because it feared that surrounding countries would fall to communism if Vietnam did.

The United States withdrew its troops from Vietnam after a strong North Vietnamese offensive during the Vietnamese new year celebration.

The United States negotiated the peaceful transition of power from colonial French administrators to popularly elected Vietnamese leaders.

The United States and the Soviet Union negotiated the division of Vietnam into separate spheres of influence that eventually became North and South Vietnam.

the fact that could also be added to column b is that during world war ii, specifically between the years 1941 and 1945, japan expanded its territory towards the indonesian territory in what was known later as part of the "pacific war". in that time, japan could conquer the philipines, singapore,   borneo, central java, malang, cebu, sumatra and various other islands of the area, therefore expanding its territory for a brief period of time.

angel island immigration station was an immigration station located in san francisco bay which worked from 1910 to 1940. the majority of immigrants that got there were from the asian hemisphere, specifically from china, japan, russia, and south asia, being china the country from where more people arrived.

the number of foreigners arriving at it took the attention of americans who feared the new arrivals would take their jobs. the work opportunities were not abundant due to the economic comedown of 1870 and the asians, as newcomers, were willing to work for cheaper wages. soon they started to be seen as a threat, which led to an increased discrimination against the chinese - the biggest ethnicity arrived at this station until 1915 when japanese immigrants outnumbered them - being considered as unsuitable americans hence their looks and social situation.

at the station, the immigrant's detention may vary depending on how long the interrogation process took: it could be weeks, months, or even years.

finally, in 1940 an explosion destroyed administration building located on the island, so the united states government decided to stop the process.

d.)   when the us left nato after the end of the cold war and they had to evolve to focus on more humanitarian measures with the smaller budget

a because the britsh thought the ameracans were trators so a