If North Korea follows through on its latest threat of setting off a nuclear explosion over the Pacific Ocean, it will ultimately be up to President Trump whether the United States will respond with military action, Secretary of State Rex Tillerson told ABC News today. ABC News Anchor David Muir asked Tillerson in an interview on "Good Morning America" about North Korea's warning that it could detonate a hydrogen bomb over the Pacific in response to Trump's speech to the United Nations General Assembly this week. "If we see this detonation of an H-bomb in the Pacific, what will the...