How did Vietnam become a single communist nation? China negotiated a settlement between North and South Vietnam that joined the two countries into a single communist nation.

North Vietnam developed a strong economy that led South Vietnam to request unification.

U. S. troops withdrew and North Vietnamese troops successfully invaded South Vietnam.

It did not become a single communist nation, but instead remained two separate countries until uniting and becoming a democracy in 2000.

China negotiated a settlement between North and South Vietnam that joined the two countries into a single communist nation.

Explanation:

Vietnam War

North Vietnam established the National Liberation Front on December 20, 1960, to foment insurgency in the South. ... The organization was dissolved in 1976 when North and South Vietnam were officially unified under a communist government.

answer: the time zones used to be whatever the local authority wanted them to be. one town might have 6am whenever the sun came up and another town had 6am 10 minutes later.  

the trains had a hard time when their orders said to be at a certain point at 6am.  

6am, but who's 6am.  

the railroads got together and set the time zones more or less along the longitude lines across the country.

explanation: