Consider the writing prompt. Write an informative, research-based essay that explains the main causes and effects of the Korean War. Which research source is both a secondary source and a source that would be relevant to the prompt? A)a book about the Korean War written by a contemporary historian B)an interview of an eyewitness to some of the major battles of the Korean War C)a speech by President Harry Truman about fighting communism through the Korean War D)an encyclopedia entry about the geography of the region where the Korean War was fought.