How is organizing history by theme different from organizing history by region? a. a historian who organizes history by theme focuses on a specific individual, whereas a historian who organizes history by region focuses on a big idea over an extended length of time. b. a historian who organizes history by theme studies a specific time period, whereas a historian who organizes history by region studies a specific individual from human history. c. a historian who organizes history by theme studies a big idea that occurs over an extended length of time, whereas a historian who organizes history by region focuses on a specific length of time. d. a historian who organizes history by theme studies a big idea that occurs over an extended length of time, whereas a historian who organizes history by region focuses on a specific area of the world.