单选题 ______ is of ten called the "backbone of North America", extending from the Northwest to the Southeast of American land.

【正确答案】 B

【答案解析】[解析] The Rocky, Mountains(落基山脉)从美国的新墨西哥州延伸到加拿大的魁北克省，因此也被称作“the great backbone of North America”或者“the Continental Divide”。