No single force has been responsible for shaping the background of American history, but of the many that have contributed, none played a more important role than the land itself.

• 以往没有哪一种单独力量是形成美国历史背景的原因，但是在所有的促成力量当中，没有比土地本身更重要的因素了（美国独特的地理优势）