Question

in october of 1950, un forces pushed the north koreans as far north as
pusan.
the yalu river.
the 38th parallel.
seoul.

Explanation:

In October 1950 during the Korean - War, UN forces advanced the North Koreans as far north as the Yalu River. Pusan is in the south of Korea, the 38th parallel was the pre - war border, and Seoul is also in the south.

Answer:

B. the Yalu River