单选题 The Louisiana Purchase of 1803 increased the territory of the United States by approximate 846,000 square miles, practically doubling the area of the United States.

【正确答案】 B

【答案解析】答案：B. approximate: approximately 分析：approximately 副词修饰句子参考译文：1803年的Louisiana购买使得美国的疆土扩大了846,000平方英里，基本上是翻倍。