valeskamartinez valeskamartinez 08-04-2015 Social Studies Answered What was the significance of the 38th parallel before the Korean War? a.When US troops moved north of it, the Chinese decided to fight. b.It was the location of the Yalu River boundary between North Korea and China. c.It served as the boundary between North Korea and South Korea. d.It marked the first site of North Korean aggression.