The correct answer is D. Secret Service agents drive dignitaries from place to place. This is because the other options are not related to the duties of Secret Service agents. Option A states that Secret Service agents take classes before they can drive the president, which is not necessarily true. Option B states that Secret Service agents learn that "code red" means "danger," which is true but not related to the duties of Secret Service agents. Option C states that Secret Service agents did not stop the killing of President Kennedy, which is true but not related to the duties of Secret Service agents.