Wall St. falls after North Korea test, Fed comments

U.S. stocks opened lower on Friday amid investor caution following a nuclear test by North Korea and comments by a U.S. Federal Reserve official that supported an interest rate hike. North Korea conducted its fifth and biggest nuclear test on Friday and said it had mastered the ability to mount a warhead on a ballistic missile, drawing condemnation from the United States as well as China, Pyongyang's main ally. "The timing of North Korea flexing their nuclear muscles is interesting in that it co