A Bethesda teenager pleaded guilty to a felony explosives charge Wednesday, admitting that he had chemicals, switches and igniters in his bedroom that readily could be made into a bomb. "We cannot know for certain what Collin McKenzie-Gude would have done if law enforcement had not acted," said U.S. Attorney Rod J. Rosenstein. "What we know for certain is that he made and exploded pipe bombs and had the components to build new explosive devices." The plea was the latest step in a case that captured national attention last year after Montgomery County officials said a map of Camp David,...